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I kind of agree with you too. As with most things, it's not black and white. It's a spectrum. And the usefulness has shifted toward the "less useful" portion of
by askafriend 11y ago
I kind of agree with you too. As with most things, it's not black and white. It's a spectrum. And the usefulness has shifted toward the "less useful" portion of the spectrum whereas in the past, mental math was far more useful and the ROI on being good at it was greater than it is in the present.
I'm not suggesting that you be totally braindead and not invest in learning the basics of mental arithmetic. I'm saying that going deeper than that initial basic investment isn't as useful today and doesn't make as much sense as in the past.
For example, I'd consider the 75^2 example in this blogpost very cool, but not worth for me to deliberately remember and so I'm not going to commit it to memory.
- shalmanese 11y agoSquares are worth knowing because a^2 - b^2 = (a+b) (a-b). This means any two numbers which are close together can be multiplied by finding the square of the midpoint. For example, 79*71 = 75^2-4^2 = 5625 - 16 = 5609. If you know your squares up to 100 and your multiplication tables up to 20, you can solve a great deal of two digit multiplication problems without having to reach for a calculator.