Question

Question 9:

Two pipes can fill a tank in 25 and 30 minutes respectively and a waste pipe can empty 3 gallons per minute. All the three pipes working together can fill the tank in 15 minutes. The capacity of the tank is:

Single Answer (+3, -1)

250 gallons

450 gallons

120 gallons

150 gallons

NextSkip

​

Answer 1

Let capacity be x gallons.

After 15 minutes

Water filled by pipe A = 15x/25

Water filled by pipe B = 15x/30

Water filled by waste pipe = -3*15 = -45

Total water filled = x = capacity

it implies

15x/25 + 15x/30 - 45 = x

6x/10 + 5x/10 - 45 = x

11x/10 - x = 45

x/10 = 45

x = 450 gallons