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ISRO Scientist Time & Work Questions with Answers & Explanations

16 Time & Work questions from the Quantitative Aptitude section of ISRO Scientist, each with the correct answer and a worked explanation. Try each question first, then tap Show answer to check. When you're ready, take the timed chapter-wise test to see your all-India rank.

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Question 1

Pipe A can fill a tank in 6 hours and pipe B can empty it in 10 hours. If both are opened together, in how many hours will the empty tank be filled?

  1. A12 hours
  2. B15 hours
  3. C3.75 hours
  4. D20 hours
Show answer
Answer: (B) 15 hours Net filling per hour = 1/6 − 1/10 = 1/15, so 15 hours.
Question 2

Pipe A can fill a tank in 12 hours and pipe B can empty it in 20 hours. If both are opened together, in how many hours will the empty tank be filled?

  1. A8 hours
  2. B7.5 hours
  3. C30 hours
  4. D35 hours
Show answer
Answer: (C) 30 hours Net filling per hour = 1/12 − 1/20 = 1/30, so 30 hours.
Question 3

A can complete a work in 15 days and B can complete it in 30 days. In how many days can they complete it working together?

  1. A12 days
  2. B9 days
  3. C10 days
  4. D22.5 days
Show answer
Answer: (C) 10 days Together they do 1/15 + 1/30 = 1/10 of the work per day, so 10 days.
Question 4

A can complete a work in 12 days and B can complete it in 36 days. In how many days can they complete it working together?

  1. A24 days
  2. B13 days
  3. C8 days
  4. D9 days
Show answer
Answer: (D) 9 days Together they do 1/12 + 1/36 = 1/9 of the work per day, so 9 days.
Question 5

Pipe A can fill a tank in 15 hours and pipe B can empty it in 20 hours. If both are opened together, in how many hours will the empty tank be filled?

  1. A5 hours
  2. B8.5714285714286 hours
  3. C65 hours
  4. D60 hours
Show answer
Answer: (D) 60 hours Net filling per hour = 1/15 − 1/20 = 1/60, so 60 hours.
Question 6

A can complete a work in 10 days and B can complete it in 15 days. In how many days can they complete it working together?

  1. A5 days
  2. B10 days
  3. C12.5 days
  4. D6 days
Show answer
Answer: (D) 6 days Together they do 1/10 + 1/15 = 1/6 of the work per day, so 6 days.
Question 7

Pipe A can fill a tank in 9 hours and pipe B can empty it in 12 hours. If both are opened together, in how many hours will the empty tank be filled?

  1. A36 hours
  2. B41 hours
  3. C33 hours
  4. D3 hours
Show answer
Answer: (A) 36 hours Net filling per hour = 1/9 − 1/12 = 1/36, so 36 hours.
Question 8

A can complete a work in 20 days and B can complete it in 30 days. In how many days can they complete it working together?

  1. A14 days
  2. B12 days
  3. C11 days
  4. D16 days
Show answer
Answer: (B) 12 days Together they do 1/20 + 1/30 = 1/12 of the work per day, so 12 days.
Question 9

Pipe A can fill a tank in 20 hours and pipe B can empty it in 30 hours. If both are opened together, in how many hours will the empty tank be filled?

  1. A57 hours
  2. B65 hours
  3. C60 hours
  4. D10 hours
Show answer
Answer: (C) 60 hours Net filling per hour = 1/20 − 1/30 = 1/60, so 60 hours.
Question 10

A can complete a work in 6 days and B can complete it in 12 days. In how many days can they complete it working together?

  1. A3 days
  2. B9 days
  3. C4 days
  4. D8 days
Show answer
Answer: (C) 4 days Together they do 1/6 + 1/12 = 1/4 of the work per day, so 4 days.

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Question 11

A can complete a work in 30 days and B can complete it in 60 days. In how many days can they complete it working together?

  1. A45 days
  2. B19 days
  3. C20 days
  4. D24 days
Show answer
Answer: (C) 20 days Together they do 1/30 + 1/60 = 1/20 of the work per day, so 20 days.
Question 12

Pipe A can fill a tank in 10 hours and pipe B can empty it in 30 hours. If both are opened together, in how many hours will the empty tank be filled?

  1. A12 hours
  2. B20 hours
  3. C7.5 hours
  4. D15 hours
Show answer
Answer: (D) 15 hours Net filling per hour = 1/10 − 1/30 = 1/15, so 15 hours.
Question 13

A can complete a work in 18 days and B can complete it in 36 days. In how many days can they complete it working together?

  1. A16 days
  2. B14 days
  3. C12 days
  4. D27 days
Show answer
Answer: (C) 12 days Together they do 1/18 + 1/36 = 1/12 of the work per day, so 12 days.
Question 14

A can complete a work in 10 days and B can complete it in 40 days. In how many days can they complete it working together?

  1. A12 days
  2. B7 days
  3. C25 days
  4. D8 days
Show answer
Answer: (D) 8 days Together they do 1/10 + 1/40 = 1/8 of the work per day, so 8 days.
Question 15

Pipe A can fill a tank in 8 hours and pipe B can empty it in 12 hours. If both are opened together, in how many hours will the empty tank be filled?

  1. A29 hours
  2. B24 hours
  3. C21 hours
  4. D4 hours
Show answer
Answer: (B) 24 hours Net filling per hour = 1/8 − 1/12 = 1/24, so 24 hours.
Question 16

A can complete a work in 10 days and B can complete it in 15 days. In how many days can they complete it working together?

  1. A12.5 days
  2. B8 days
  3. C6 days
  4. D10 days
Show answer
Answer: (C) 6 days Together they do 1/10 + 1/15 = 1/6 of the work per day, so 6 days.

These are RankerClub practice questions written in the ISRO Scientist pattern. They are not official SSC/IBPS/RRB papers.

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