SBI PO 20 June 2015 Paper

B is 25% more efficient than C.
∴ Ratio of time taken by B and C
= 100 : 125 = 4 : 5
Time taken by B = 4x days
Time taken by C = 5x days
∴

1

4x

+

1

5x

=

3

40

⇒

5+4

20x

=

3

40

⇒

9

20x

=

3

40

⇒

3

x

=

1

2

⇒ x = 6
Time taken by B = 24 days
Time taken by C = 30 days
If the time taken by A be y days,
then

1

y

+

1

24

=

7

72

⇒

1

y

=

7

72

−

1

24

=

7−3

72

=

4

72

=

1

18

∴ y = 18
∴ (A + C)’s 1 day’s work
=

1

18

+

1

30

=

5+3

90

=

8

90

=

4

45

∴ Time taken by A and C together
=

45

4

= 11

1

4

days