A) 180
B) 150
C) 120
D) 60
Correct Answer: C
Solution :
[c] Let third pipe can emptied the tank in x min. \[\therefore \]1 min work of pipe\[A=\frac{1}{20}\] 1 min work of pipe\[B=\frac{1}{24}\] and 1 min work of pipe\[C=\frac{1}{x}\] \[\therefore \] \[\frac{1}{20}+\frac{1}{24}-\frac{1}{x}=\frac{1}{15}\] \[\Rightarrow \] \[\frac{1}{x}=\frac{1}{20}+\frac{1}{24}-\frac{1}{15}=\frac{1}{40}\] \[\therefore \] \[x=40\] Hence, capacity of tank\[=40\times 3=120\]gallon |
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