Three valves, when opened individually, can drain the water from a cer

Question

Three valves, when opened individually, can drain the water from a certain tank in 3, 4, and 5 minutes respectively. What is the greatest part of the tank that can be drained in one minute by opening just two of the valves?

(A) 3/20
(B) 1/5
(C) 7/12
(D) 2/3
(E) 3/4

Show Answer

Official Answer

C

(A) 3/20
(B) 1/5
(C) 7/12
(D) 2/3
(E) 3/4

imeanup · Answer

LCM(3,4,5)=60
When working together with the greatest part of the tank that it can drain is  \frac{(3+4+5)}{60}=\frac{12}{60}=\frac{1}{5}

IMO  Ans B

DanielSoderlunds · Answer

Greatest part is to open the two fastest tanks that do the job in 3 and 4 hours respectively.

1/3+1/4==4/12 + 3/12 = 7/12 -> Answer C

Anki2609 · Answer

Three valves, when opened individually, can drain the water from a certain tank in 3, 4, and 5 minutes respectively.

Work done by each valve per minute :
Valve 1 =  \frac{1}{3} 
Valve 2 =  \frac{1}{4} 
Valve 3 =  \frac{1}{5}

What is the greatest part of the tank that can be drained in  one minute by opening just two of the valves

Valve that works faster = Valve 1 and Valve 2.
to find the maximum work done. We need to calculate the total work done by Valve 1 and Valve 2 = \frac{ 1}{3 }+ \frac{1}{4}
 
=   \frac{7}{12}  (C) is the answer

divyadna · Answer

Let total capacity of the tank be 60 U ( LCM of 3,4, and 5).

Valve 1 drains 60/3= 20U/min
Valve 2 drains 60/4= 15U/ min
Valve 3 drains 60/5= 12 U/ min
Valve 1 and valve 2 are faster than valve 3 and together drain 35U/ min.
So, the greatest part of the tank that can be drained in one minute by opening just two of the valves= 35/60= 7/12
Option C is the answer

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Three valves, when opened individually, can drain the water from a cer

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Three valves, when opened individually, can drain the water from a cer

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