X can do 1/4 of work in 10 days, Y can do 40% of the same work in 40 days and Z can do 1/3 of the work in 13 days. Who will complete the work first?

Time taken to complete the work by X =10 x 4 = 40 = 40 days
Time taken to complete the work by Y = (40 x 100)/40 = 100 days
Time taken to complete the work by Z = 13 x 3 = 39 days
Hence, Z will complete the work first.