19 is only 1 away from 20, so you prefer to start by multiplying 20 times 5, which equals 100. Then we need to take away a squadron of 5, because there are actually only 19 squadrons, not 20. 100 take ...

Is There a Way to Square 2-Digit Numbers Quickly? While it’s easy to calculate the squares of single-digit numbers like 5 in your head (since those squares are part ...

Multiplication is a fundamental skill in mathematics, but some number combinations can appear tricky. Imagine being able to quickly multiply numbers like 35 x 35 or 65 x 65 in your head, almost ...

こんにちは！「100日後にそろばん完全マスター！」の主です。 Youtube47日目の動画「そろばん6級 3桁×2桁・2桁×3桁のやり方」の内容を簡単に解説します。 ちなみに、速く答えを出せる「両落とし」と呼ばれる方法で解説していて、そろばん界のドンである ...