Grade 4 Olympiad Maths Challenge Day 10 #quiz #maths #exam #olympiadmaths #olympiad #learnwithnaum

[00:00:00]So, this question comes from an Olympiad topic on Roman numerals. Welcome back to day 10 of the 60-day math challenge. So, here's the question. Question 10. Which of the following has five at 10's place?

[00:00:14]Option A, DXLV. Option B, CCCLVIII.

[00:00:19]Option C, CDXXV.

[00:00:22]Option D, DCLXVI.

[00:00:25]Let's solve it step by step. Pause the video if you need more time. Step one, let's check option A first. DXLV. Let us break it. D equals to 500. XL equals to 40. Why 40? Because when a smaller numeral comes before a larger numeral, we subtract. As X equals to 10 and L equals to 50, so we will subtract X from L. XL equals to 50 minus 10 equals to 40. Therefore, XL equals to 40. Now, V equals to five. So, D plus XL plus V, that is 500 plus 40 plus five equals to 545.

[00:01:03]The 10's digit here is four. Therefore, this is not the right answer. Step two, let us check option B. CCCLVIII.

[00:01:13]When numerals are written from largest to smallest, we add them. C equals to 100. So, CCC equals to 100 plus 100 plus 100 equals to 300. L equals to 50. V equals to five. I equals to one. So, VIII equals to five plus one plus one plus one equals to eight.

[00:01:36]Now, CCC plus L plus VIII. That means 300 plus 50 plus eight equals to 358.

[00:01:45]The 10's digit is five. This matches the question. So, the correct answer is option B. Did you get it right?

[00:01:53]Friends, I'm nine years old and I work hard to create these math videos every day. Your likes, comments, and subscriptions encourage me to keep going. Thank you for your support, and I will see you in day 11 of the 60-day math challenge.