Question

In a fish tank, 65% is female fishes. The rest are male. Female fishes are also 15 less than twice of male fishes. How many female fishes and male fishes in the tank ? (Set up the rational equation and solve for x)

Answer 1

• 195 female fish
• 105 male fish

Explanation:

Let x be the number of male fish. Then 2x-15 is the number of female fish, and the ratio of female to male fish is ...

0.65/0.35 = (2x -15)/x . . . . . rational equation

13/7 = 2 - 15/x . . . . . . . . . . . . simplified

15/x = 2 -13/7 = 1/7 . . . . . . . . add 15/x - 13/7

x = 7·15 = 105 . . . . . . . . . . . . multiply by 7x

2x-15 = 210 -15 = 195 . . . . . . use the expression for the number of females

There are 195 female fish and 105 male fish in the tank.