Multiple choice

A and B together can complete a work in 12 days, A alone can complete it in 20 days. If B now does the work only for half a day daily, then the number of days required to complete the work by A and B together is- A और B मिलकर एक कार्य को 12 दिन में पूरा कर सकते हैं। A अकेले उसे 20 दिन में पूरा कर सकता है। अब यदि B प्रतिदिन केवल आधे दिन कार्य करता है, तो A और B को मिलकर कार्य पूरा करने में कितने दिन लगेंगे?

  1. 18

  2. 15

  3. 14

  4. 16
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A+B's combined rate: 1/12 work/day. A's rate: 1/20 work/day. So B's rate: 1/12 - 1/20 = 1/30 work/day. When B works half-days, effective rate = 1/20 + (1/2)(1/30) = 1/20 + 1/60 = 4/60 = 1/15 work/day. Time needed: 15 days. Option A (18 days) overestimates. Options C, D are incorrect.

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