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SBI PO 30 April 2017 Papers
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© examsnet.com
Question : 46
Total: 100
Time taken by A alone to finish a piece of work is 60% more than that taken by A and B together to finish the same piece of work. C is twice as efficient as B. If B and C together can complete the same piece of work in 13
1
3
days, in how many days can A alone finish the same piece of work?
36
24
16
28
Other than those given as options
Validate
Solution:
C is twice as good as B.
∴ If time taken by B be 2x days,Time taken by C = x days
∴
1
2
x
+
1
x
=
3
40
⇒
1
+
2
2
x
=
3
40
⇒
3
2
x
=
3
40
⇒ 2x = 40 ⇒ x = 20
∴ Time taken by B = 40 days
If A takes y days, then
y =
(
1
1
y
+
1
40
)
×
160
100
⇒ y =
(
1
40
+
y
40
y
)
×
8
5
⇒
5
8
y =
40
y
40
+
y
⇒
y
8
=
8
y
40
+
y
⇒ 40 + y = 64
⇒ y = 64 - 40 = 24 days
OR
B : C = 2 : 1
Time taken by both in doing work =
40
3
∴ Time taken by B =
40
3
× 3
= 40 days
Time taken by C =
40
3
×
3
2
= 20 days
Again,
A
+
B
A
=
160
100
=
8
5
⇒ 5A + 5B = 8A
⇒ 3A = 5B
⇒ A : B = 5 : 3
∴ Time taken by A =
3
5
× 40
= 24 days (inverse ratio)
© examsnet.com
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