I'm not good at math, but here is a simple math trick. Suppose you wanted to know 7% of 80? Just multiply seven time eight, with is 56, so we know the answer is 5.6. Since percentages are derived from multiplication, 5.6 is also 80% of 7.
20% is easy to derive in your head. If the bill is $90 and you want a 20 percent tip, you know it is 18, 13.50 for 15%.
Suppose you want to know 12% of 35. The first thing I would do in my head is say that 10 percent is $3.5, and then add .7 to that, for 4.2.
I think everyone watching a basketball or American football game know how many points one team is ahead of another without pulling out a calculator.
1 comment:
I’m very quick when it comes to calculating, and at various times all three of my children (now 23, 19, and 17) have asked me how come I’m so good at it. It’s clear to me: calculating baseball stats when I was a kid!
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