12% of 75 without breaking a sweat

Question

Solve in your head. What is 12\% of 75? Aim: under 5 seconds.

Accepted Answer

The direct route is a little awkward (10\% of 75 is 7.5, plus 2\% is 1.5, giving 9). The swap trick is cleaner because 75\% is just three-quarters: 12\% 	ext{ of } 75 = 75\% 	ext{ of } 12 = 	frac{3}{4}	imes 12 = 9. Takeaway. Before grinding through blocks, check whether the other number becomes a nice fraction: 75\% = 	frac34, 50\% = 	frac12, 25\% = 	frac14, 20\% = 	frac15. Swapping a\% of b into b\% of a often turns the problem into a one-step fraction.

12% of 75 without breaking a sweat

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