35% of 60, in one breath

Question

Solve in your head. What is 35\% of 60? Aim: under 5 seconds.

Accepted Answer

Build 35\% from blocks: 35\% = 3 	imes 10\% + 5\%. - 10\% of 60 is 6, so 30\% is 18. - 5\% is half of 10\%: 3. 18 + 3 = 21. Cross-check with the swap trick: 35\% of 60 = 60\% of 35 = 0.6 	imes 35 = 21. Same answer. Takeaway. Any "tens-plus-a-five" percentage is quick: multiply the 10\% block up, then add the 5\% half-block. And keep the swap in your back pocket as an independent check.

35% of 60, in one breath

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