Why do this problem?
requires logical and creative thinking. It is also an intriguing and challenging way to practise addition and subtraction.
A clock face without hands is a useful introduction for these challenges and it is a good idea to suggest that all the lines are drawn between the numbers rather than from number to number.
Let learners have a go at the first part of the challenge in pairs without saying very much and then after a suitable length of time, bring them together to talk about how they went about finding a solution. Some might have used a trial and improvement approach; others may have found the total of all the numbers on the clock face first and then used some trial and improvement. Discussing
strategies at this stage will help children with the other parts of the problem.
You can download this sheet of clock faces to give to the class for rough working, jotting and recording.
What are the totals you are trying to get?
How do you know?
What is the sum of all the numbers on the clock face?
Pupils could explore other divisions of the clock face and find the time on the clock when the hands do the dividing into different groups of numbers.
You could draw a line across a clock face and ask children to add the numbers on each side to show what is required. Having a calculator available would help if the addition is causing a problem in itself.