The ratio of orange fish to blue fish in an aquarium is 2:3. If there are a total of 50 fish, how many of them are blue?
2 k + 3 k = 50 ... k = 10
blue fish = 3 * 10
O = orenge fishs
B= blue fishs
The ratio of orange fish to blue fish in an aquarium is 2:3 means:
O / B = 2 / 3
Cross multiply:
3 O = 2 B
Divide both sides by 3
O = 2 / 3 B
There are a total of 50 fish means:
O + B = 50
Replace O with 2 / 3 B in this equation.
2 / 3 B + B = 50
2 / 3 B + 3 / 3 B = 50
5 / 3 B = 50
Multiply both sides by 3
5 B = 150
B = 150 / 5 = 30
30 of them are blue
Check result:
B = 30
O = 2 / 3 B
O = 2 / 3 • 30
O = 60 / 3 = 20
20 of them are orange
O / B = 20 / 30 = 10 • 2 / 10 • 3 = 2 / 3
O + B = 20 + 30 = 50