Stage: 3 Challenge Level: 
There are some water lilies in a lake.
The area that they cover doubles in size every day.
After 17 days the whole lake is covered with water lilies.
How long did it take them to cover half the lake?
Calculating with fractions. Patterned numbers. Integers. Multiplication & division. Number - generally. Fractions. Mathematical reasoning & proof. Factors and multiples. Properties of numbers. Place value.
Published November 2004,December 2004.
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