Question:
A pipe can fill a tank in 6 hours, and another pipe can empty it in 8 hours. If both are opened together, how long will it take to fill the tank?
A pipe can fill a tank in 6 hours, and another pipe can empty it in 8 hours. If both are opened together, how long will it take to fill the tank?
Show Hint
For pipes, combine rates (positive for filling, negative for emptying) to find net rate.
Updated On: Mar 23, 2026
- 12 hours
- 24 hours
- 36 hours
- 48 hours
Show Solution
Verified By Collegedunia
The Correct Option is B
Solution and Explanation
- Step 1: Filling pipe rate = $\frac{1}{6}$ tank/hour, emptying pipe rate = $-\frac{1}{8}$ tank/hour.
- Step 2: Net rate = $\frac{1}{6} - \frac{1}{8} = \frac{4 - 3}{24} = \frac{1}{24}$ tank/hour.
- Step 3: Time to fill = $\frac{1}{\text{Net rate}} = \frac{1}{\frac{1}{24}} = 24$ hours.
- Step 4: Verify: In 24 hours, filling pipe fills $24 \times \frac{1}{6} = 4$ tanks, emptying pipe empties $24 \times \frac{1}{8} = 3$ tanks, net = 1 tank.
- Step 5: Option (2) is 24 hours, correct.
- Step 2: Net rate = $\frac{1}{6} - \frac{1}{8} = \frac{4 - 3}{24} = \frac{1}{24}$ tank/hour.
- Step 3: Time to fill = $\frac{1}{\text{Net rate}} = \frac{1}{\frac{1}{24}} = 24$ hours.
- Step 4: Verify: In 24 hours, filling pipe fills $24 \times \frac{1}{6} = 4$ tanks, emptying pipe empties $24 \times \frac{1}{8} = 3$ tanks, net = 1 tank.
- Step 5: Option (2) is 24 hours, correct.
Was this answer helpful?
0
0
Top CAT Quantitative Aptitude Questions
- In a triangle ABC,AB=AC=8cm. A circle drawn with BC as diameter passes through A. Another circle drawn with center at A passes through B and C. Then the area,in sq.cm,of the overlapping region between the two circles is
- The simple interest accrued on an amount of Rs.25,000 at the end of three years is Rs.7,500. What would be the compound interest accrued on the same amount at the same rate in the same period?
- What is the sum of all roots of the equation \(|x+4|^2–10|x+4|=24\)?
- A solid metal sphere is melted and smaller spheres of equal radii are formed. 10% of the volume of the sphere is lost in the process. The smaller spheres have a radius which is \(\frac{1}{9}\text{th}\) the larger sphere. If 10 litres of paint were needed to paint the larger sphere,how many litres are needed to paint all the smaller spheres?
- The ratio of the ages of a husband and his wife when they got married was 6:5. 4 years and 6 years after their marriage they had their 1st and 2nd children. The sum of the present ages of the husband and wife is 6.4 times the sum of the present ages of their children. The average age of the family at present is 18.5 years. Find the ratio of the ages of the husband and wife when their second child was born.
View More Questions
Top CAT Time and Work Questions
- A and B can do a work in 20 days. When A works at 60% capacity, B has to work at 150% capacity to finish the work. Find in how many days the faster one will finish the work alone.
- At their usual efficiency levels, A and B together finish a task in 12 days. If A had worked half as efficiently as she usually does, and B had worked thrice as efficiently as he usually does, the task would have been completed in 9 days. How many days would A take to finish the task if she works alone at her usual efficiency?
- Three men and eight machines can finish a job in half the time taken by three machines and eight men to finish the same job. If two machines can finish the job in 13 days, then how many men can finish the job in 13 days?
- A cyclist leaves A at 10 am and reaches B at 11 am. Starting from 10:01 am, every minute a motor cycle leaves A and moves towards B. Forty-five such motor cycles reach B by 11 am. All motor cycles have the same speed. If the cyclist had doubled his speed, how many motor cycles would have reached B by the time the cyclist reached B?
- John jogs on track A at 6 kmph and Mary jogs on track B at 7.5 kmph. The total length of tracks A and B is 325 metres. While John makes 9 rounds of track A, Mary makes 5 rounds of track B. In how many seconds will Mary make one round of track A?
View More Questions
Top CAT Questions
- Compare and contrast between Portia and Jessica characters in Merchant of Venice.
- In a triangle ABC,AB=AC=8cm. A circle drawn with BC as diameter passes through A. Another circle drawn with center at A passes through B and C. Then the area,in sq.cm,of the overlapping region between the two circles is
- The simple interest accrued on an amount of Rs.25,000 at the end of three years is Rs.7,500. What would be the compound interest accrued on the same amount at the same rate in the same period?
- What is the sum of all roots of the equation \(|x+4|^2–10|x+4|=24\)?
- A solid metal sphere is melted and smaller spheres of equal radii are formed. 10% of the volume of the sphere is lost in the process. The smaller spheres have a radius which is \(\frac{1}{9}\text{th}\) the larger sphere. If 10 litres of paint were needed to paint the larger sphere,how many litres are needed to paint all the smaller spheres?
View More Questions