A person X can complete 20% of work in 8 days and another person Y can complete 25% of the same work in 6 days. If they work together, in how many days will 40% of the work be completed?
Answer & explanation
Answer: (a) 6
X would finish the whole work in 40 days and Y in 24 days, so together they do 1/40 + 1/24 = 1/15 of it each day. 40% of the work therefore takes 0·4 × 15 = 6 days.
- X: 20% in 8 days, so 100% in 40 days. Y: 25% in 6 days, so 100% in 24 days.
- Together per day: 1/40 + 1/24 = 3/120 + 5/120 = 8/120 = 1/15.
- Whole work together = 15 days; 40% of it = 0·4 × 15 = 6 days.
- Check: in 6 days X does 6/40 = 15% and Y does 6/24 = 25%; total 40%.
Remember · Convert partial work to full-job time first, add daily rates, then scale to the fraction of work asked.
Question and answer: UPSC's official GS Paper II (2020, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·