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# Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in

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Joined: 02 Sep 2009
Posts: 55801
Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in  [#permalink]

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07 Jan 2019, 04:04
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Difficulty:

15% (low)

Question Stats:

78% (01:23) correct 22% (01:48) wrong based on 62 sessions

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Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in 2 hours, how many minutes will it take both pipes to fill 2/3 of the tank?

A. 30
B. 48
C. 54
D. 60
E. 72

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Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in  [#permalink]

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Updated on: 08 Jan 2019, 01:47
2
Bunuel wrote:
Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in 2 hours, how many minutes will it take both pipes to fill of the tank?

A. 30
B. 48
C. 54
D. 60
E. 72

combined rate ' 1/3+1/2 = 5/6
time 6/5 * 60 = 72
2/3 * 72 = 48 mins IMO B

or say
180 mins and 120 mins

1/180 + 1/120 ; 5/360 ; 72 mins
2/3 * 72 = 48 mins IMO B
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Originally posted by Archit3110 on 07 Jan 2019, 04:15.
Last edited by Archit3110 on 08 Jan 2019, 01:47, edited 2 times in total.
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Posts: 55801
Re: Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in  [#permalink]

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08 Jan 2019, 01:43
Archit3110 wrote:
Bunuel wrote:
Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in 2 hours, how many minutes will it take both pipes to fill of the tank?

A. 30
B. 48
C. 54
D. 60
E. 72

Bunuel : answer choice given seems to be incorrect correct option should be e 72.

combined rate ' 1/3+1/2 = 5/6
time 6/5 * 60 = 72 IMO E

or say
180 mins and 120 mins

1/180 + 1/120 ; 5/360 ; 72 mins E ..

Sorry Archit. There was a copy/paste error. Corrected question reads: how many minutes will it take both pipes to fill 2/3 of the tank? Edited. Thank you.
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Re: Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in  [#permalink]

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12 Mar 2019, 10:09
1
Total work to be done is LCM(2,3) = 6 units.
A can do 3 units in 1 hour.
B can do 2 units in 1 hour.
Together they can do 5 units in 1 hour.
They require 6/5 hours to fill the tank completely.
To fill 2/3 of the tank, they require 2/3*6/5*60 min = 48 min.

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Re: Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in  [#permalink]

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12 Mar 2019, 10:14
IMO B .

together they can fill full tank in 6/5 hours = 72 mins .

so 2/3 tank will fill in 72*2/3 = 48 mins

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Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in  [#permalink]

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12 Mar 2019, 10:14
Considering x as the capacity of the tank

Flow rate of pipe A per minute: $$\frac{x}{(3*60)}=\frac{x}{180}$$

Flow rate of pipe B per minute: $$\frac{x}{(2*60)}=\frac{x}{120}$$

Flow rate of both pipes working together:

$$\frac{x}{120}+\frac{x}{180}=\frac{5x}{360}=\frac{x}{72}$$

$$\frac{x}{72}*t=\frac{2*x}{3}$$

$$t=48min$$

Ans B
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Re: Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in  [#permalink]

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12 Mar 2019, 10:26
Bunuel wrote:
Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in 2 hours, how many minutes will it take both pipes to fill $$\frac{2}{3}$$ of the tank?

A. 30

B. 48

C. 54

D. 60

E. 72

combined rate = 1/3+1/2 = 5/6
so for 2/3 filling
2/3 = 5/6 * time * 1/60
so
time = 2*6*60/3*5 = 48
IMO B
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Re: Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in  [#permalink]

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12 Mar 2019, 18:10
I think question is edited now. Because previously 2/3rd was written as 2323.
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Re: Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in  [#permalink]

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14 Mar 2019, 17:01
Bunuel wrote:
Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in 2 hours, how many minutes will it take both pipes to fill $$\frac{2}{3}$$ of the tank?

A. 30

B. 48

C. 54

D. 60

E. 72

The rate of pipe A is 1/3, and the rate of pipe B is 1/2. We let n = the time that the two pipes work together to fill 2/3 of the tank and create the equation:

(1/3)n + (1/2)n = 2/3

Multiplying by 6, we have:

2n + 3n = 4

5n = 4

n = 4/5 hour = 48 minutes

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Re: Pipe A can fill a tank in 3 hours. If pipe B can fill the same tank in   [#permalink] 14 Mar 2019, 17:01
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