A person X can complete 20% of work in 8 days and another person Y can complete 25% of the same work in 6…
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?
6
8
10
12
Solution
X completes 20% in 8 days, so X completes 100% in 40 days; X's rate $= 1/40$ per day. Y completes 25% in 6 days, so Y completes 100% in 24 days; Y's rate $= 1/24$ per day. Combined rate $= 1/40 + 1/24 = 3/120 + 5/120 = 8/120 = 1/15$ per day. Time for 40% of work $= 0.4 / (1/15) = 0.4 \times 15 = 6$ days.