15 men or 30 women can do a piece of work in 60 days. In how many days can 20…
2024
15 men or 30 women can do a piece of work in 60 days. In how many days can 20 men and 10 women do thrice the work?
Answer: C. 108 — Key idea: find daily work rates from the given data, then use the combined rate to find the time for three jobs. Total work = 15 men × 60 days = 900 man-days…
- A.
98
- B.
100
- C.
108
- D.
112
Attempted by 19 students.
Show answer & explanation
Correct answer: C
Key idea: find daily work rates from the given data, then use the combined rate to find the time for three jobs.
Total work = 15 men × 60 days = 900 man-days (treat this as 1 complete job).
One man's daily work = 1/900 of the job. From 30 women × 60 days = 1800 woman-days, one woman's daily work = 1/1800 = 1/2 of a man's daily rate.
Combined daily work of 20 men and 10 women = 20×(1/900) + 10×(1/1800) = 20/900 + 10/1800 = 25/900 = 1/36 of the job per day.
Time to do one job = 1 ÷ (1/36) = 36 days. For three jobs = 3 × 36 = 108 days.
Answer: 108 days.