A completes 80% of a work in 20 days. Then B also joins and A and B together…
2026
A completes 80% of a work in 20 days. Then B also joins and A and B together finish the remaining work in 3 days. How long does it need for B if he alone completes the work?
- A.
35
- B.
35.5
- C.
40
- D.
37.5
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Correct answer: D
Let total work = 100 units.
A completes 80 units in 20 days, so A's rate = 80/20 = 4 units/day.
Remaining work = 20 units.
A and B together finish the remaining 20 units in 3 days, so combined rate = 20/3 units/day.
B's rate = combined rate − A's rate = 20/3 − 4 = 8/3 units/day.
Time for B alone to complete 100 units = 100 ÷ (8/3) = 100 × 3/8 = 37.5 days.
Answer: 37.5 days