Answer:
The third number is 1/60
Step-by-step explanation:
Let the denominator of the number = x
1/4 + 1/3 + 1/x = 1/5
1/4 + 1/3 = 3/12 + 4/12 = 7/12
The lowest common denominator is 60x.
(7/12 + 1/x)/3 = 1/5 Remember that this is the average of 3 numbers. That's what the 3 is doing on the left. Multiply both sides by 3
7/12 + 1/x = 3/5 Multiply through by 60x
35x + 60 = 36x
x = 60
Very nice problem. Thanks for posting. This problem is a little involved. If you have trouble with it, leave a note in the comments and I'll come back and discuss it.
