A Tank, Which Usually Takes 5 Hours to be Filled, Takes 6 Hours to Fill Because of a Leak GMAT Problem Solving

Question: A tank, which usually takes 5 hours to be filled, takes 6 hours to fill because of a leak. Find the time in which the leak can empty the tank if it is filled and the inlet pipe is shut.

  1. 30 hours
  2. 27.5 hours
  3. 25 hours
  4. 22.5 hours
  5. 20 hours

Correct Answer: A


Solution and Explanation:
Approach Solution 1:

Given: A tank, which usually takes 5 hours to be filled, takes 6 hours to fill because of a leak
Find out: Find the time in which the leak can empty the tank if it is filled and the inlet pipe is shut
Let us assume that the Tank has a capacity of: 120 L

- The usual time taken to fill the the tank is 5 hours
Hence, in one hour, the tank fills: 120/5 = 24 Liter/hour.

- Time taken to fill the the tank with leak is 6 hours
Hence, time taken to fill the the tank with leak is 120/6 = 20 L/hour

- The flow of leakage is (24 - 20 = 4 Litre/hour).

- Now, time in which the leak can empty the tank if it is filled and the inlet pipe is shut

=> Hence, total litre divided by 4.
= 120/4
= 30 Hours

Approach Solution 2:
Given: A tank, which usually takes 5 hours to be filled, takes 6 hours to fill because of a leak
Find out: Find the time in which the leak can empty the tank if it is filled and the inlet pipe is shut

From the provided information, we understand that in 6 hours, the leak drains 1/5 of tank
Once the inlet is shut, the time in which the tank can be emptied is:
=5*6 hours
=30 hours

Approach Solution 3:
Let x be the time taken leak to empty the full tank
fraction of tank filled by inlet pipe in one hour = 1/5 ( in no leakage)
fraction of tank emptied by leak hole in one hour = 1/x
Tank capacity = 1 unit
(1/5 - 1/x) * 6 = 1 ( in the presence of leak it takes 6 hours to fill the tank)
solving for x we get, x = 30 hours

A tank, which usually takes 5 hours to be filled, takes 6 hours to fill because of a leak.”- is a topic of the GMAT Quantitative reasoning section of GMAT. The question has been taken from the book “The Official Guide for GMAT Review.” To solve GMAT Problem Solving questions a student must have knowledge about a good amount of qualitative skills. GMAT Quant practice papers improve the mathematical knowledge of the candidates as it represents multiple sorts of quantitative problems.


 

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