Here goes. There is actually an easy way to calculate perfect squares for relatively large numbers. For example, to calculate 13² , we only need to multiply 10( 13-3) and 16 (13+3), then add 3² to it, and tada, we get 169. ( take the digit in the ones place, ie 3 in this case) And this works for all. (: Try it! I think this is super ingenious. I think this is going to work wonders if we need to do mental calculations fast. Who needs a calculator? Haha. Yeah and for my brief glimspe through it, it teaches us how to multiply 3 digit numbers by 2 digit numbers mentally too , amazing man!

Yeah, I am definitely going back to buy this book, " Think like a math genius". Cool (:

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