UPSC CSE Prelims 2016
To determine who completes the work first, the total time each individual takes to complete 100% of the work must be calculated.
Z can do 1/3 of the work in 13 days. Therefore, Z can complete the entire work in 13 × 3 = 39 days.
Comparing this with the time taken by W, X, and Y, Z completes the work in the shortest duration.
The time taken by other individuals to complete the entire work is calculated as follows:
Since W takes 120 days, X takes 40 days, and Y takes 100 days, all these durations are longer than the 39 days taken by Z. Therefore, W, X, and Y do not complete the work first.