AFCAT Model Paper 4

GIVEN:
Saral, Ravi and Karan alone takes 10, 12 and 15 days, respectively to complete a task.
FORMULA USED:
Time = Work / Efficiency
CALCULATION:
Saral, Ravi and Karan alone takes 10, 12 and 15 days
Efficiency of Saral =

1

10

units
Efficiency of Ravi =

1

12

units
Efficiency of Karan =

1

15

units
Suppose the number of days taken to complete the task is ‘a’.
Saral worked for 2 days, Ravi worked for (a - 3) days and Karan worked for a days.
Now,

2

10

+

(a−3)

12

+

a

15

=1
⇒

1

5

+

a

12

−

1

4

+

a

15

=1
⇒3

a

20

=1+

1

20

⇒3

a

20

=

21

20

⇒ a = 7
∴ Number of days taken to complete the task = 7 days