UPSC Prelims 2024·CSAT·Quantitative Aptitude·Time and Work

A, B, C working independently can do a piece of work in 8, 16 and 12 days respectively. A alone works on Monday, B alone works on Tuesday, C alone works on Wednesday; A alone, again works on Thursday and so on. Consider the following statements: 1. The work will be finished on Thursday. 2. The work will be finished in 10 days. Which of the above statements is/are correct?

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Last updated 8 Jul 2026, 4:39 pm IST
  1. A1 OnlyCorrect
  2. B2 Only
  3. CBoth 1 and 2
  4. DNeither 1 nor 2

Explanation

Here's a brief explanation:

  1. Calculate Total Work and Efficiencies:

    • A takes 8 days, B takes 16 days, C takes 12 days.
    • The Least Common Multiple (LCM) of 8, 16, 12 is 48 units. This is our total work.
    • A's efficiency = 48/8 = 6 units/day
    • B's efficiency = 48/16 = 3 units/day
    • C's efficiency = 48/12 = 4 units/day
  2. Track Work Done Day by Day:

    • Day 1 (Monday, A): 6 units. Total = 6
    • Day 2 (Tuesday, B): 3 units. Total = 9
    • Day 3 (Wednesday, C): 4 units. Total = 13
    • Day 4 (Thursday, A): 6 units. Total = 19
    • Day 5 (Friday, B): 3 units. Total = 22
    • Day 6 (Saturday, C): 4 units. Total = 26
    • Day 7 (Sunday, A): 6 units. Total = 32
    • Day 8 (Monday, B): 3 units. Total = 35
    • Day 9 (Tuesday, C): 4 units. Total = 39

    Remaining work = 48 - 39 = 9 units.

    • Day 10 (Wednesday, A): A works and does 6 units. Total = 39 + 6 = 45 units.

    • Remaining work = 9 - 6 = 3 units.

    • Day 11 (Thursday, B): B works and does 3 units. Total = 45 + 3 = 48 units.

  3. Evaluate Statements:

    • Statement 1: The work will be finished on Thursday. This is correct. The work is completed on Day 11, which is a Thursday.
    • Statement 2: The work will be finished in 10 days. This is incorrect. The work is finished on Day 11.

Therefore, only statement 1 is correct.

The final answer is A) 1 Only.

Quantitative Aptitude: A, B, C working independently can do a piece of work in 8, 16 and 12 days respectively. A alone works on Monday, B alone

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