Children sometimes use the wrong operation to solve problems. Cramer et al XXXXXXXXXXasked some young adults to solve this problem: ‘Sue and Julie were running equally fast around a track. Sue started...

Children sometimes use the wrong operation to solve problems. Cramer et al. (1993) asked some young adults to solve this problem: ‘Sue and Julie were running equally fast around a track. Sue started first. When she had run nine laps, Julie had run three laps. When Julie completed 15 laps, how many laps had Sue run?’

■ What is the answer to this problem? ■ What is the ratio between Sue’s and Julie’s number of laps? ■ What other answers do you think would be given and why? ■ If you want to know more about this problem, go to Figure 7.13 on page 217.