Divide 8600 by 25 without dividing

Question

Solve in your head, no long division. What is 8600 \div 25? Aim: under 5 seconds.

Accepted Answer

Dividing by 25 is the same as multiplying by 4 and dividing by 100 (because 25 = 100/4): \frac{8600}{25} = \frac{8600 	imes 4}{100} = \frac{34400}{100} = 344. Quadrupling is two easy doublings (8600 	o 17200 	o 34400), and dividing by 100 just moves the decimal point. Takeaway. Swap awkward divisors for easy multiplications: \div 25 	o 	imes 4 / 100, \div 5 	o 	imes 2 / 10, \div 50 	o 	imes 2 / 100, \div 125 	o 	imes 8 / 1000. Doubling a couple of times beats long division every time on a speed test.

Divide 8600 by 25 without dividing

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