A man completes 7/8 of a job in 21 days. How many more days will it take him to finish the job if quantum of work is further increased by 50%?
Answer & explanation
Answer: (d) 15
He does 1/8 of the job every 3 days, so the whole job takes 24 days. When the job grows to 1.5 times its size, 5/8 of the original job remains, which takes 15 more days.
- 7/8 of the job in 21 days, so the whole job takes 21 ÷ 7/8 = 24 days (1/24 of the job per day).
- The work is increased by 50%, so the total becomes 1.5 jobs.
- Work left = 1.5 − 7/8 = 12/8 − 7/8 = 5/8 of the original job.
- Days needed = 5/8 × 24 = 15.
- Check: 7/8 + 15/24 = 7/8 + 5/8 = 12/8 = 1.5 jobs.
Remember · Turn work done into a daily rate first; then express the remaining work as a fraction of the original job.
Question and answer: UPSC's official GS Paper II (2021, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·