Tool By Zeal Point

Q. Two taps can fill a tank in 80 minutes and 120 minutes, respectively. If both taps are opened together, in how many minutes will the tank be filled ?

Solution

Assume the capacity of the tank = 1 (whole tank).

1st Tap:

It fills the tank in 80 minutes.

$Work done in 1 minute = 1/80$

Second tap:

It fills the tank in 120 minutes.

$Work done in 1 minute = 1/120$

Together:

$1/80 + 1/120$

LCM of 80 and 120 = 240

$= 3/240 + 2/ 240 = 5/240 = 1/48$

So, both taps together fill: $1/48$ of the tank in 1 minute.

Therefore, the tank will be filled in: $48 minutes$

Trick

$Time = T1\timesT2 / T1+T2$ $= 80 \times 120 / 80+120 = 9600/200 = 48 minutes$

Ans: 48 minutes

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PRACTICE SET – Pipes & Cisterns

Q1. Two taps can fill a tank in 60 minutes and 90 minutes, respectively. If both taps are opened together, how long will they take to fill the tank ?

(A) 30 minutes (B) 36 minutes (C) 40 minutes (D) 45 minutes

Q2. Two pipes can fill a tank in 40 minutes and 60 minutes, respectively. If both are opened together, in how many minutes will the tank be filled ?

(A) 20 minutes (B) 24 minutes (C) 30 minutes (D) 25 minutes

Q3. Two taps can fill a tank in 50 minutes and 75 minutes, respectively. If both taps are opened together, how long will they take to fill the tank ?

(A) 25 minutes (B) 30 minutes (C) 35 minutes (D) 40 minutes

Q4. Two pipes can fill a tank in 72 minutes and 120 minutes, respectively. If both pipes are opened together, how long will they take to fill the tank ?

(A) 40 minutes (B) 45 minutes (C) 48 minutes (D) 50 minutes

Q5. Two taps can fill a tank in 80 minutes and 160 minutes, respectively. If both taps are opened together, in how many minutes will the tank be filled ?

(A) 40 minutes (B) 50 minutes (C) 53⅓ minutes (D) 60 minutes

Trick

For two filling pipes/taps: $Time = T ^{1} \times T ^{2 / T 1 + T 2}$

Pipes and Cisterns : Questions PYQ

Trick