Question

P and q can do a piece of work in 10 days and 20 days respectively. Both of them start the work but p leaves the work 5 days before its completion. Find the time in which work is completed

Answer 1

P takes 10 days to completion of the work and q takes 20 days for the completion of the work and P leaves this work before 5 days of completion of this work it means Q will take double of its to completion of the work it means which work can be completed in 10 + 20 is equal to 30 days which will complete in 35 days

Answer 2

Answer-

P alone can do in - 10 days

Q alone can do in -20 days

(Using the LCM method we take LCM of 10 and 20 which is 20 and then calculate the efficiency)

Efficiency of P = 2

Efficiency of Q =1

Let the work gets completed in X days

So

Before the last 5 days P and Q work is 3(X-5)

Where 3 is the efficiency

During last 5 days there is only Q and his work is -    5×1

Where 1 is the efficiency

3(X-5)+1×5=20

X=10 days

Ans-10 days