Two pipes can fill a tank in 20 and 24 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:  Pick:	A) 228gallons	B) 267gallons	C) 120gallons	D) 767gallons	E) 167gallons
Explanation:   Work done by the waste pipe in 1 minute ={\color{Black} \frac{1}{15}-\left ( \frac{1}{20}+\frac{1}{24} \right )=\left ( \frac{1}{15}-\frac{11}{120} \right )=-\frac{1}{40}} [-ve sign means emptying]   Volume of {\color{Black} \frac{1}{40}} part = 3 gallons   Volume of whole = (3 x 40) gallons = 120 gallons.   Answer: 120gallons
<result>C</result>
Two pipes can fill a tank in 20 and 24 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: