What is 35% of 80?

Question

Any percentage can be assembled from 10% chunks and a half-chunk. Solve in your head. What is 35\% of 80? Aim: under 8 seconds.

Accepted Answer

Start from 10\% of 80 = 8. Then 30\% = 24 and 5\% = 4 (half of 10%): 35\% = 30\% + 5\% = 24 + 4 = 28. So 35\% of 80 = \mathbf{28}. Check via the commuting trick: 35\% of 80 = 80\% of 35 = 28. Same. Takeaway. Get 10\% (move the decimal), scale it, and add a 5\% half-step. This scaffolding handles any percentage on the fly.

What is 35% of 80?

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