Although most people can read times from an analogue clock mistakes are sometimes made with conversions to 24 hour clock and problems involving time difference.

Don’t forget that there is no a.m. or p.m. when using the 24 hour clock and that you need to add or subtract 12 from the hours to carry out conversions.

When carrying out time difference problems people sometimes try to reach for a calculator. Remember that calculators work in base 10 but time is based on 60’s. I have found that the ‘counting’ on method is the most successful

A number line can greatly help to work out time difference problems.

By adding the 1 hour and the 15 and 22 minutes it can be seen that the answer is 1 hour 37 minutes.