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. Integers. Mathematical reasoning & proof. Multiplication & division. Patterned numbers. Fractions. Factors and multiples. Place value. Number - generally. Properties of numbers.
Published November 2004,December 2004.
Copyright © 2007. University of Cambridge. All rights reserved.
NRICH is part of the family of activities in the Millennium Mathematics Project, which also includes the Plus and Motivate sites.
email: nrich@damtp.cam.ac.uk