Multiply 2846 by 5 without multiplying

Question

Solve in your head, no long multiplication. What is 2846 	imes 5? Aim: under 5 seconds.

Accepted Answer

Multiplying by 5 is the same as multiplying by 10 and halving: 2846 	imes 5 = \frac{2846 	imes 10}{2} = \frac{28460}{2} = 14230. Appending a zero then halving is far easier than the usual column multiplication, and halving an even number like 28460 is instant. Takeaway. Trade a 	imes 5 for a 	imes 10 then halve: 	imes 5 	o 	imes 10 / 2, 	imes 25 	o 	imes 100 / 4, 	imes 50 	o 	imes 100 / 2. On a timed arithmetic screen these swaps shave seconds off every "times five" question.

Multiply 2846 by 5 without multiplying

Your answer

More Mental Math questions