Multiplying and Dividing Whole Numbers

You need to be really happy doing multiplications and divisions without a calculator - they’re likely to come up in your non-calculator exam.

The Traditional Method:

1) Split it into separate multiplications.

2) Add up the results in columns (right to left).

EXAMPLES
1. Work out 46 × 27

46 × 27 = (40 × 20) + (40 × 7) + (6 × 20) + (6 × 7) = 800 + 280 + 120 + 42 = 1242.

2. Work out 243 × 18

   243 × 18 = (240 × 10) + (240 × 8) + (3 × 10) + (3 × 8) = 2400 + 1920 + 30 + 24 = 4374.

There are lots of other multiplication methods - make sure you’re comfortable using whichever method you prefer.

EXAMPLE

What is 748/22?

For questions like this, it’s useful to write out the first few multiples of the number you’re dividing by.

E.g. 1 × 22 = 22 2 × 22 = 44 3 × 22 = 66 4 × 22 = 88

Short Division Method

1) Set out the division as shown 22/748

2) Look at the first digit under the line. 7 doesn’t divide by 22, so put a zero above and look at the next digit. 0

3) 22 × 3 = 66, so 22 into 74 goes 3 times, with a remainder of 74 - 66 = 8.

4) 22 into 88 goes 4 times exactly.

So 748/22 = 34 with a remainder of 0.