                 Quick Answer:Their weights are: = 2 pounds = 3 pounds = 4 pounds

Complete Solution:

There are many ways to solve this problem.

 Stategy #1: Add the weights on all 3 scales, so,  +  +  = 18 pounds This means that: + + = 9 pounds But from Scale #2 we know that: + = 7 pounds So subtract and find: = 2 pounds Since the little fish weighs 2 pounds, and we know from Scale #3 that: + = 5 pounds then, = 3 pounds Also, from Scale #1, + =  6 pounds So, = 4 pounds
 Stategy #2: If you put the fish with weights 6 and 7 together on the scales, then + +  = 13 pounds But we know from Scale #3, + = 5 pounds Subtract and find, + =  8 pounds So, = 4 pounds

Strategy #3
Consider the weights in the two balloons showing 6 and 7. The weights differ by one pound and the big fish is on both scales, so the medium fish weighs 1 pound more than the little fish. The third scale shows that the combined weights of the little fish and medium fish is 5 pounds. Since the medium fish weighs 1 pound more than the little fish, the little fish must weigh 2 pounds and the medium fish 3 pounds.     Home · Back to the Challenge · Try These · Think About This  ·  Did You Know? · Resources Try Another Challenge · Challenge Index · Math Index · Printing the Challenges · En Español Family Corner · Teacher Corner · About Figure This! · Purchase the CD  ©2004 National Council of Teachers of Mathematics Web site and CD-ROM design/production © 1999-2004 KnowNet Construction, Inc.    