Work out the following without a calculator.

0.5 × 9 × 10

It is possible to carry out the multiplication in the order it is written. So, as 0.5×9=4.5 the calculation becomes 4.5×10=45.

However, as multiplication is commutative, it can be done in a different order.

You may find it easier to do the multiplication like this: 0.5×10×9. As 0.5×10=5 the calculation becomes 5 × 9 = 45.