CSEC Math Monday 25th November 2024 Consumer Arithmetic Part 3

Added: 2026-05-09

[00:00:02]all right so let's get started consumer arithmetic part three and today we're going to be doing currency conversion but what is um what is currency conversion right a currency conversion is like when you what convert what um Trinidad dollars to US dollar or or or or basian dollars the Jamaican dollars and whatnot but anyway take take down the um take down the topic and we're going to do a few questions all right so you're going to have to take down the question right don't start the question as yet I wanted to do this question with you so everyone take down the question with ginger there right take a two minutes take it down and we will work this first one out together as a team ginger has 80 U s dollar and wants to converted to TT and of course there must be an exchange rate now the exchange rate changes every once in a while a long time ago one US was 7t and and and it it has changed over the years it's not it's no longer 7 TT for one us I believe it's $6 and a certain amount of cents but in the exam The Examiner has to give you the rate so for my particular question you'll see it in green being here $1 is the same thing as $640 so how do I do currency conversion questions I still do it like this up to today I go in the bank and I draw up a cross like this and I ask myself what are the two currencies that I'm dealing with well we're dealing with us so I call one column us and I call the other one TT but that's the other one we're dealing with and in the first row I put the conversion rate given to us by The Examiner The Examiner said one US is equivalent to what $6.40 now you're going to need your calculators today so everyone do that for me draw across and Puttin the rate that was given to You by The Examiner right this is going to be super simple with the cross then the examiner um then you asks itself well um how much us did they give us well remember only us could go in this column he gave us 80 Us in in question that's how much ji has um ginger has sorry and we want to convert it to what TT so we put the X here so all we need to do now is cross multiply to solve for X now I know some of you all could have done this a simpler way but take my advice learn this way so when the question gets complex and it has tricks in it this table will always give you the correct answer for the trick questions and for the hard questions so let's cross multiply 1 by X is X that's good news because one by anything is itself and then you take $680 and you multiply it by 80 so 80 multi by $640 I'm getting what this amount of money um $512 now to get full marks in the exam remember we were finding TT so you have to put the TT now right so the examiner knows that you're talking about the TT dollars so that's the that's the answer for part a real real simple right I'm going to put the answer back here right right now that's the end of part e what part B do you think when you go to the bank and you ask them hey change this money know they just do it for free how much of you all believe that that the bank will do something for free for you what are the chances of that never all right right so the bank was will not do it for free so they will charge a conversion fee and in this particular Bank they're charging you 5% of the money so when you exchange the money and you get the $512 they don't give you the $512 they say who hold on hold on you cannot get the five the whole $512 we will be taking 5% of that money before we hand it over to you so for Part B the bank is going to take 5% so how much how do we find 5% of something by now everybody knows we put 5 over 100 and we multiply by the 512 work out that for me the the bank is going to take 5% of your money that is their Fe work out that small piece for me quickly on your calculator tell me what you get all right let's see here 5 over 100 multip by 5 12 I'm getting this now you got to write it properly right remember it's money we're talking about here so it's $25 60 um somebody read it wrong on the calculator it's $25.60 not $256 look at it properly it's 5 / 100 multip by 5 12 now this here is the bank fee so but the question didn't ask how much is the bank feel they ask how much will Ginger have left so if Ginger thought he was getting $512 and then oh yeah had to put TT here correct and then the bank took $26.50 how much will he be left with and and that's the final answer for B because they ask you for how much he's left with right that is what he walks home with so take the um $512 and minus the $25.60 and I'm getting this in TT let me know if you're seeing the same thing 4864 and 40 cents and I put my TT so there's no mix up and whatnot all right so everyone try this one now right it's almost the same thing but instead of saying Bank fee I said tax now a tax and a fee is almost the same thing in this particular case a ta a fee is when they take away something from you and a tax is the same thing all right so good luck with this one it's the same basic type of question is just to make sure you understood the first question good luck and you have I'll give you five minutes to take down the question and also provide the two answers for A and B so let's see what's going on here you have okay I think some people just assume that the value has to be larger than the 120 right so um let's see if the value actually comes up larger or not right it's two types of currency it comes in TT and EC now someone asks if we exchange it like if we put the EC in this column and the TT in the other column would we get the same answer yeah we'll get the same answer you can put it TD first or EC it really really doesn't matter you just have to make sure and put the correct exchange rate okay so remember it's one EC so the one have to go by the EC right if they say EC is one the one have to go under EC and the TT is $320 okay great so and they gave us how much TT 120 and we want to converted to EC so let's see what happens here right so$ and for 3.2 you can put 3.2x we multiply here and you have 1 by 120 is 120 so you throw across the multiply you get a divide let's see 120 ided by 3.2 H I'm getting $37 and 50 c now I going put the correct units here right remember we converted to EC do right and it's $37.50 you have to make sure put the correct units as well you'll be surprised how examiners would just slice away marks for not doing simple things like that okay so we have B now it's a tax they're going to come up with right it's a tax now so they're going to charge you 2% tax no all right not a problem how do you find 2% of something it's two over 100 and remember this is the amount of EC we think he leaving with but that is not how much he going to leave with because they're going to take 2% of that so you multiply that by two divide it by 100 it seems to me they're going to be taking not much 75 cents look at correct so far guys they taking 75 cents from him check it back guys some people did it wrong it's to divided by 100 multip by the 3750 we dealing we don't care about the TT now we we care about the EC we EC land now right so to figure out how much he has left we take the 5750 which he thought he was going to leave with and the bank tell us say whoa whoa whoa hold up hold up we're going to take 75 cent so and this is how this is my final answer that I'm getting here this is how much he leaving with right $36.75 A lot of people got it but for those who got it wrong right um tell me what you did wrong now I'm interested in a small mistake it was supposed to be be $37.50 all right so let me show you how this game here works right so jiy needs to make it to the other side where the crystal is so he has to jump on the blocks you have to make three choices choose a letter choose one number and choose a color I'll of course only one combination is going to be correct so choose one letter a number and a color and let's see if jiby our protagonist will be able to make it across clearly I have too much time on my hands y so it's always good so let's see what happens so ji is going to fall jump on the first set of blocks Oh e block a turned on fire so B was the proper choice right B was the proper Choice he has to jump on the next block which one would be the good one when he jumps to the next row oh two had a snake two had a snake so one was the correct choice and let's see the the yellow and blue when he jumps on The Next set oh the blue had a scorpion so guys the correct comb ination the correct combination was B one and yellow how much of you all made it all was bad that is real bad luck oh boy ah somebody said they made it right Julian you made it all right so all right let's move on all right try this one now no one should get this one wrong now here's another word that is used processing fee that's the same exact thing right so you had three questions to get it correct right three chances and this is the third chance good luck and I hope everyone gets it correct this rup not too sure all right so it's two currencies we're dealing with right jmd Jamaican dollars and TT dollars right so according to this the Jamaican dollars is one and the TT dollar is 45 that's the rate given to us by The Examiner the GMD is one 50 and we want to convert it to what TT so 1 by X is X and this by this let's see 150 by 045 I'm getting that it's TT right so we have put TT this $67.50 I think a few people need to check back this right um it's just a matter of multiplying the 150 by the4 five in this particular question so now we have um $67.50 but the bank is saying that they're going to take 12% of that money so let's find 12% 12 over 100 by $67.50 cents right it's multiply by 67 and we getting a nice value we getting $810 I mean that that's not the end of the question but that that is how much the bank is going to take from you so now how much uh how much is fzo left with he thought he was leaving the bank with $67.50 and buam they take1 $810 so the amount he's left wh is let's see ah not bad um $59.40 that's my final answer for Part B look for your mistakes look for your mistakes right so take down this topic um this question and well this is simple interest like I said simple interest real easy just some minor tricks I for those who can't remember it from sea I'll quickly refresh your memory um when it comes to the formula right so don't panic too much for simple interest and this is the The Examiner has to say whether it's simple interest or compound interest but the formula that I'm giving you here is for simple interest interest is principle by rate by time over a 100 now in the I is for interest the interest is just the extra amount you get when you invest in the bank that's just the extra amount that's different from the total amount one thing you have to remember when we using this formula the time has to be in years it must must be in years so this question is a pretty straightforward question the principal is the amount they put in the bank in the first place that's the investment so the in the principal is 1,200 so we put 1 12200 to replace P the rate is the percentage you can't miss that that's the 5% and the time you have to make sure they give you it in years sometime they just try to trick you and give you it in months make sure to convert it to years so it's two divided by 100 work this out but the question is not finished work out the interest the interest let me see for those who want to show what to do right I'm getting 100 $20 which a lot of people are telling me now the reason that is not the final answer is because they ask for how much money will he have I put B by mistake but he have at the end of the two years so what's the total amount remember the total amount is the interest plus the original amount he put in the bank which is the principal so it's 120 that's the extra plus the 1200 so it's actually what 1320 sorry for the bad handwriting there right but it's 13 no what I corre yeah 1320 a lot of people just sent 120 as the final answer they didn't ask you for the interest they ask you for the total amount he had okay right so take down everything you need to take down and we will move now is this question now read this question properly it's a reverse question right so Captain America has decided to invest his money in the hero Bank whatever that is right but this question is not asking you for the interest it's asking you for the rate see if you can do this question um I'll give you a hint you'll end up cross multiplying good luck f is the same formula we're using so interest is what principle by rate by time because they did say it was simple interest in the question look at there let's um let's put in some values now now they told it us the they gave us the interest the interest was 120 so we're going to replace I with 120 that is the interest the principal is how much um he invests 800 so that's how much he putting in the first place so that's is a principle we don't know the rate but they gave us the time in years for over 100 so we could cross what multiply but before we cross multiply and we can simplify this and we can multiply the eight by the four then just before we cross multiply cuz 8 by 4 I is 3200 or something like that let me just move up here I have 120 on one and I'm going to multiply the 800 by 4 think that's ti200 and don't forget Mr R there you think you for those who didn't know what to do you think you could cross multiply now and solve for or you should be able to take it from there right take a minute and let's see if you can if I see more correct answers coming plenty plenty correct answers let's see The Final Answer here all right so when we multiply here you're going to get to2 200 multip by R because anything multiply by one is itself 120 by 100 is 120 with two extra zeros we then what we solving for R right so this 3200 is a multiply throw him across we get a divide and remember you're rate will be a percent so you have to make sure put the percentage sign in the exam otherwise you'll lose a mark right let me see I'm getting 3.75% that's the answer right 3.75% make sure they W TW the 12 on top have three zeros make sure you're seeing that right A lot of people put the wrong units they put dollars but I thought we were finding rate rate is a percent so you can't put dollars right The Examiner will frown upon that somebody said I have a extra Zero by the 120 oh no no no no I I don't think I have a mistake I think I good day right all right so for those who got it wrong you think you understand this one actually this actually um this actually comes in sea but it is used a different technique to do it because then sea kids would know about cross multiplication right but we just use cross multiplication in high school to figure out questions like this all right take a 10 seconds take down what you need to take that and we will move on right so Melvin the vampire strange name for for a vampire interest the reason it's strange is not for the reason you think it's because simple interests and compound interests use the same exact formula but how can that be if simple interest and compound interest is two different types of interests shouldn't they have different formulas the answer is no they have the same formulas you just use them different for example if this was a simple interest question if if and they ask me for how much money the person had at the end of the two years well then I just use this this formula right principle by rate by time over 100 my principal is 1,200 look at in the question here the rate is five and since are asking me for two years I put two here I'll work it out and that's the extra money I have at the end of two years but it's not simple interest you see in simple interest if they tell it the time is two years you replace the te with two if they tell you the time is 3 years you replace the te with three just like in primary school but here's the thing about compound interest the time is always one year strange I I don't care if the examiner told you if it's 4 years at in the bank the time the number you replace with time is always one so how do we work this out well for compound interest we have to work it out one year at a time if it's two years we have to do two piece of calculation if it's three years we have to do three pieces of calculation so let's start off since it's two years we have to start off with one year so we put down the formula interest is principle by rate by time over 100 well for this question the principle we started off with 12 12200 so put 1200 the rate is five and how much is time remember I now said in compound interest the time is always one could we all work out the interest after the first year after the first year what's the interest after the first year 1,00 by 5 by 1 ided 100 I'm getting $60 let me know if you're seeing that on your calculator I'm getting $60 great now remember that is just the interest What's the total amount he has at the end of the first year remember he put in 1,200 and he got an extra $60 so his total amount in the bank now at the end of the first year is $1,260 things looking good his money is going up ironically this doesn't happen in a real bank if for those who have money in a bank you realize for some reason your money always get less and less all right so let's let's move to year two now for year two we going to use the same formula principle by rate by time over 100 but there's a small trick the rate is still 5% time is always one I don't care that we are in year two time is always one but the principle is no longer $1,200 the principle is the new amount we have remember leaving year one he had 1260 the new principle is 1260 so that's how compound interest is different the principle always changes the principle is always the previous amount you had not the amount that you had at the beginning beginning beginning of the question not always the principle can change through out the question so calculate his new interest what is his new interest I'm getting what $63 but so how much is the total amount he have now what do we add this 63 to the original 1,200 or the new amount the 1260 the one he left here one with what do we add the 63 to we added to the 1260 in year two it come like the 1200 don't exist anymore the new principle is 1260 so the answer would be 1260 + 63 and this is the am 1 3 2 three so you see how compound interest are a little bit different all right so this one is a little bit harder you have to do the calculation for three years keep in mind the previous answer gets transferred to the next year so if you get one year wrong since you're using the answer from the previous year it's like a domino effect you get one wrong everything else after is wrong I just want to know how much Atom Man here has at the end of three years that's all I want to know okay good luck give you five minutes with this one air one compound interest so interest is principal by rate by time over 100 I don't care what year I am in if it's compound interest time is one the rate is four and the original amount is 180 that's my principle so let's get this 180 by 4 by 1 / 100 the first interest is $720 I hope I have that correct which means the I put a for amount right the total amount now is 180 plus the $720 which is $1 18720 this is the new principle right and that's the principle that will go over to what year two that $180 does not exist anymore only that 187.5 okay right so let's move on to year two interest is principle by rate by time over 100 time is always one in compound interest the rate is still four but the new principle is 18720 so let's work out the new interest but the interest for year two at least $1 18720 um guys um how I got the $7 guys anybody disagrees with my 720 here all I did was 180 multip by 4 multiply by one and then divide it by 100 anybody disagrees with that I I double checking it I think I have it correct 180 by 4 by 1 n that correct so for the person who telling me wrong just double check your working now you may have just typed it wrong in your calculator right so let's work out this one now for year two the new principle is 18720 ulti by 4 by 1 remember time is always one so by one now you got to be careful here for my interest I'm getting $7 and this is how much of you all seen that on your calculator but we have to round it off to what two decimal places right right yeah you have to put0 49 not 48 the bang go lock you up canot do that right that's stealing a or your 1 C off right you're going if you get lock up you're going to get fired or something like that or a St talking to by your manager right something is going to happen so how much is the total amount now remember the amount from the previous year was the $1 18720 plus you get an extra $749 add up these two 187.000 plus $749 anybody seen this at the end of year too 19469 C we good there guys check back your there's only so much I could do um remember for this one is just 180 multiply I have the numbers on top here right it's just a matter of typing in the numbers and dividing it by 100 right I'm 100% sure correct so you need to type it in back correct on your calculator all right so double check your working if you didn't get it right and remember if I Wrong real people will be tell chat now so you have it wrong so you have it wrong that then I'll double check but if one person tell me wrong most likely I just raise my eyebrow and be like I think the student need to check it over in that case okay all right right so let's see what's going on with year three don't worry they won't give you four years in the exam they won't give you four years no exam are going to be so wicked right for year three we go back to the same formula principle by rate by time over 100 time is still one no matter what right rate is still four and the new principle remember the new amount we have is1 19 9469 so let's work out the new interest this is what I get when I round it off right when I round it off properly to two decimal places 7.79 that's the interest which makes the total amount now what's the amount we had from before1 469 and we add $779 so let's see what we get here 194 plus 69+ 7.79 and real people sent me this answer but some people with some decimal points off which makes me think you're round off somewhere wrong along the question look for a mistake now guys all the working is on the screen follow the working and point out to me way went WR I really wanted them oh well you all deserve a little small um brain relaxer here all right so Jimmy goes to another caveman here and tries to steal his um well fire here because fire is a precious thing in those times so what you need to do is choose two items just two and if they end up being the same color well you win the fire choose two item let's see if you get lucky here guys let's see if you get lucky any two items give the Rock and the fruit the spare and the Sabertooth the SC fish any [Music] [Music] to do I items you have to choose then not one two items the two have to be the same car nobody like the insect now I can't remember this one so I'll play with you guys also I'm going to choose so since nobody choosing the insect I'm going to choose the insect and the bird nobody has chosen that combination so I will choose that all right let's see you guys got lucky it's going to change color oh I did not win cuz my insect is yellow and my bird is blue anybody got lucky for those who won you'll notice ji's um torch there it's going to light up ah he has the fire all right let's go let's go congratulations to those who won right no one should get this one wrong now right no one right quickly get your final answer for the third year fast as possible fast like that superhero in the corner there right let's go correct good news um interest is principle by rate by time over 100 so the principle is I think it's just $200 the rate is eight and time is always one always always one 200 by 8 by1 divided by 100 I'm getting $16 interest at the end of the first year so My total amount is 200 that's the original amount plus 16 but that's easy to add in my head right $216 and this will be transferred to year two as my new principal so my $200 doesn't really exist here anymore my new principal from this point is $216 so interest is principal by rate by time over 100 the new principal is 216 in rate is eight and time is one always one 216 by 8 by 1 divided by 100 I'm getting this $1 1728 so my new amount is the2 200 $6 which was my new principal plus the extra $17.28 and I'm getting this for my new principal or new amount 2 three 3.28 so that value now I'm going to carry it across to year three interest it's principal by rate by time over 100 let me see the new principle is 2 to the 3.28 rate is e and time is one there we go this one I think we might have to round off the interest is 1866 so how much is the new amount Now 23 3.28 Plus the 1866 23 3.28 + 1866 this is my final answer 25194 if you had round off properly again $251 94 if you got it correct feel really good about yourself right compound interest questions don't come harder than this right if you got it wrong but you see a mistake you know take it as a win right right right take it as a win if you understand it is about ah so next week we're going to start with wages and taxes all right so right so we ending class today right all right so um so for those who are just in if you want um let's let's scrolling through the question right so next week is wages and taxes and we'll start that next week all right guys so thanks for coming out today right for those who have turned test good luck good luck