Three carpenters P, Q and R are entrusted with office furniture work. P can do a job in 42 days. If Q is 26% more efficient than P and R is 50% more efficient than Q, then Q and R together can finish the job in approximately:

P is doing a job in 42 days. In one day, he does 1/42 of the work.

Q is more efficient than P by 26%.

Then, the part of work that Q does in one day is: $$\frac{1}{42}$$ x 1.26 = 3/100

R is more efficient than Q by 50%.

Then, the part of work that R does in one day is: $$\frac{3}{100}$$ x 1.5 = 9/200

If Q and R are put together then part of work they will finish in a day is:

$$\frac{3}{100}$$ + $$\frac{9}{200}$$ = $$\frac{15}{200}$$ 

Hence total work can be done in 200/15 = 13.33 days $$\cong$$ 13 days