What is 16% of 25? (Use the swap)

Question

"16% of 25" sounds fiddly, until you swap the two numbers. Solve in your head. What is 16\% of 25? Aim: under 6 seconds.

Accepted Answer

Percentages commute: a\% of b = b\% of a. So flip to the easy order: 16\% 	ext{ of } 25 = 25\% 	ext{ of } 16 = \frac{16}{4} = 4. So 16\% of 25 = \mathbf{4}. Computing a quarter of 16 is instant; computing 16% of 25 directly is not. Takeaway. a\% of b = b\% of a, always test whether the flipped version is easier. Here 25\% = "divide by 4" saves all the work.

What is 16% of 25? (Use the swap)

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