Multiple choice

B does half of the work in comparison to A in 1 7 of the time taken by A. If both take total 21 days to complete a work, then how many days will B alone take to complete that work? A द्वारा लिए गए समय के 1 7 समय में B, A की तुलना में आधा कार्य करता है। यदि एक काम को पूरा करने के लिए दोनों को कुल 21 दिन लगते हैं, तो B अकेला उसी काम को पूरा करने के लिए कितने दिन लेगा?

  1. 26

  2. 27

  3. 28

  4. 32
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B Correct answer
Explanation

Let A alone take a days and B alone take b days. A's work rate is 1/a, B's is 1/b. B does half work in (1/7) of A's time, so (1/2)/(1/b) = (1/7)×(1/(1/a)), giving b/a = 2/7. Together: 1/a + 1/b = 1/21. Substituting a = 7b/2 gives 2/7b + 1/b = 1/21, so b = 27 days.

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