Time and work
- A and B can do a work in 18 days, B and C in 24 days, and A and C in 36 days. How many days will A alone take? Answer: B. 48 days Answer: (B) 48 days Work = 72 units. A+B = 4, B+C = 3, A+C = 2 units/day. So A+B+C = 9 ÷ 2 = 4.5 units/day. A = 4.5 − (B+... 1
- 3 men and 4 boys can do a work in 11 days, while 4 men and 3 boys can do it in 10 days. How many days will 2 men and 1 boy take? Answer: B. 22 days Answer: (B) 22 days Let a man do m and a boy b of the work per day. 3m + 4b = 1/11 and 4m + 3b = 1/10 . Adding: 7(m + b)... 1
- A is twice as efficient as B. B starts a work alone and works for 5 days; then A joins him and together they finish the work in 5 more days. How many days would A alone take for the whole work? Answer: D. 10 days Answer: (D) 10 days Let B do 1 unit/day; then A does 2 units/day. Work = B's 5 days + (A+B) for 5 days = 5 × 1 + 5 × 3 =... 1
- A can do a work in 12 days and B in 15 days. They work together for 4 days and then both leave. C finishes the remaining work in 6 days. How many days would C alone take for the whole work? Answer: D. 15 days Answer: (D) 15 days Work = 60 units; A = 5, B = 4 units/day. In 4 days they do 36 units; 24 units are left. C does 24 uni... 1
- A can do a work in 25 days and B in 20 days. They start together, but A leaves 5 days before the work is finished. In how many days is the work finished? Answer: B. 131/3 days Answer: (B) 131/3 days Let the total time be T days. A works (T − 5) days and B works T days. T - 5/25 + T/20 = 1 → 4(... 1
- A can finish a piece of work in 12 days and B can finish it in 18 days. In how many days will they finish it working together? Answer: C. 71/5 days Answer: (C) 71/5 days Work per day = 1/12 + 1/18 = 3 + 2/36 = 5/36 . Time = 36/5 = 71/5 days. 1