P can do 1/4 th of work in 10 days. Q can do 40% of work in 40 days and R can do 1/3 rd of work in 13 days. Who will complete the work first ?

Answer: Option C

P complete $$\frac{1}{4}$$ th of work in 10 days
So, P will complete the whole work in 40 days.
Q completes $$\left(40\%=\frac{2}{5}\text{th}\right)$$   work in 40 days
Q will complete the whole work in = $$\frac{40\times 5}{2}$$ = 100 days
R completes $$\frac{1}{3}$$ work in 13 days
R will complete the whole work in = 39 days
Work will be finished firstly by the man who will take less days to complete it,
So, R will complete it first.