Ever wanted to impress everyone by solving complex multiplication problems in your head, without needing a pencil or paper? It's not magic; it's mental math—a superpower you can learn! This article is ...

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 ...