Trick 35:🧠 Mind-blowing maths trick!Learn how to multiply 5×99 and 5×999 in seconds 📚

追加: 2026-05-28

A mental math trick for multiplying 5 by numbers ending in 9s: For 5 × 99, subtract 1 from 99 to get 98, then append 5 to get 985; for 5 × 999, subtract 1 from 999 to get 998, then append 5 to get 9985. This method works because 5 × (100 - 1) = 500 - 5 = 495, but the shortcut provides a faster mental calculation approach.