18% of 250, instantly

Question

Solve in your head. What is 18\% of 250? Aim: under 5 seconds.

Accepted Answer

Two clean routes, pick whichever you see first. Route 1, the swap trick. a\% of b equals b\% of a, and 250\% is easy: 18\% 	ext{ of } 250 = 250\% 	ext{ of } 18 = 2.5 	imes 18 = 45. Route 2, blocks. Build 18\% from tens and ones: - 10\% of 250 is 25. - 5\% is half of that: 12.5. - 1\% is 2.5, and you need three of them: 7.5. 25 + 12.5 + 7.5 = 45. Takeaway. Whenever one of the two numbers turns into a friendly multiplier, use the swap: a\% of b = b\% of a. Otherwise fall back on 10\%, 5\%, and 1\% blocks. Both should land you on 45.

18% of 250, instantly

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