Quick
Answer:Their weights are:

= 
2
pounds 

= 
3
pounds 

= 
4
pounds 


Complete
Solution:
There are many ways to solve this problem.

Add the weights on all 3 scales, so,


+ 

+ 

= 
18 pounds 


+ 

+ 

= 
9 pounds 
But from Scale #2 we know that:

+ = 7
pounds 

= 2
pounds 
Since the little fish
weighs 2 pounds,
and we know from Scale #3 that:

+ = 5
pounds 

= 3
pounds 

+ =
6 pounds 

= 4 pounds 


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 

+ =
8 pounds 

= 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. 
