Stage: 2 Challenge Level: 
Nina must cook some pasta for 15 minutes. The only way she has of measuring time is a 7-minute sand-timer and an 11-minute sand-timer.
How can she use these timers to measure exactly 15 minutes?
Practical Activity. Trial and improvement. Investigations. Interactivities. Working systematically. Addition & subtraction. Factors and multiples. Visualising. Combinations. Multiplication & division.
Published May 2000.
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