Multiplying using double and halve

When multiplying two numbers together, if you double one of the numbers and halve the other, you will get the same answer, but this might be an easier sum to do.

Example: 16 x 3 = 8 x 6 = 48 (where we halved 16 and doubled 3)

Example: 22 x 5.5 = 11 x 11 = 121 (where we halved 22 and doubled 5.5). This example shows it can be a very useful way of dealing with fractions.

Of course, we arent restricted to doubling: if you can multiply one number by 3 and divide the other by 3 it works just as well, as it would for 4, 5 10 or anything else.

Example: 8 x 1.75 = 2 x 7 = 14 (where we quartered 8 and quadrupled 1.75).