AFCAT Model Paper 1

Given:
A and S working alone can complete a work in 20 and 30 days respectively
Working together, S left the work 5 days before completion.
Formula used:
The efficiency of a person is the inverse of the time taken
Calculation:
According to the question:
Per day efficiency of A=

1

20

Per day efficiency of S=

1

30

Working together, per day efficiency =

1

20

+

1

30

⇒

(3+2)

60

=

5

60

=

1

12

Let together they worked for d days
Then, total work gets completed in d + 5 days
⇒

d

12

+

5

20

=1
⇒

d

12

=

3

4

⇒ d = 9
Now, d + 5 = 14
∴ Total work gets completed in 14 days.