Measures in the primary curriculum

Exploring time - part 2

Do not use formal subtraction algorithms for finding the length of time from one recorded time to the next; teach an ad hoc adding-on approach.

For example, to find the length of time of a journey starting at 10.45 a.m. and finishing at 1.30 p.m. draw a time number line and reason like this: 15 minutes to 11 o’clock, then 2 hours to 1 o’clock, then a further 30 minutes, making a total of 2 hours and 45 minutes.

Setting this out as a formal subtraction would be highly inadvisable. But representing it as a calculation on a number line as shown in would be highly advisable.

Learning about time is also complicated by the fact that the hands on a conventional dial-clock go round twice in a day.