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RRB Junior Engineer Stage 1 Model Papers 3
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© examsnet.com
Question : 3
Total: 100
A, B and C can do a piece of work in 10, 12 and 15 days respectively. A leaves 5 days before the completion of the work and B leaves 2 days after A. The whole work lasts for
7 days
6 days
12 days
13 days
Validate
Solution:
Suppose, the work was finished in x days. Then A‘s (x – 5) day‘s work + B‘s (x – 3) day‘s work+ C‘s x day‘s work = 1.
⇒
x
−
5
10
+
x
−
3
12
+
x
15
=
1
⇒
6
(
x
−
5
)
+
5
(
x
−
3
)
+
4
x
=
60
⇒
6
x
−
30
+
5
x
−
15
+
4
x
=
60
⇒
15
x
=
60
+
30
+
15
⇒
15
x
=
105
⇒
x
=
7
days
.
© examsnet.com
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