Multiply 56 by 125 without multiplying

Question

Solve in your head, no columns. What is 56 	imes 125? Aim: under 8 seconds.

Accepted Answer

Since 125 = 1000/8, multiplying by 125 means multiplying by 1000 and dividing by 8: 56 	imes 125 = \frac{56 	imes 1000}{8} = \frac{56000}{8} = 7000. The clean route is to divide first: 56 / 8 = 7, then attach three zeros for 7000. Takeaway. Treat 125 as 1000/8: multiplying by 125 is "divide by 8, then shift three places." Dividing by 8 is halving three times, and spotting that 56 is a multiple of 8 makes the whole thing a one-step lookup.

Multiply 56 by 125 without multiplying

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