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24 Jun 2017, 03:02
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C
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Difficulty:
35%
(medium)
Question Stats:
71% (02:05) correct
29%
(02:29)
wrong
based on 230
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Sam can repair a machine in 15 days and Ross can repair the same machine in 25 days. If they decide to repair the machine on alternate days, with Ross on the first day, followed by Sam on the second day and so on till the repair is completed, how many days do they take to complete the repair work.
A) 17
B) 18
C) 19
D) 20
E) 21
A) 17
B) 18
C) 19
D) 20
E) 21
24 Jun 2017, 04:08
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Work done by Sam in one day = 1/15, in Ross = 1/25.
Total work done by Sam in the first day and Ross in the second day = 1/15 + 1/25 = 8/75.
No. of days to complete the work: n(8/75) = 1
n = 75/8 = 9.375.
So, it will take 9.375 two day's work, hence 9.375 * 2 = ~19 days.
Total work done by Sam in the first day and Ross in the second day = 1/15 + 1/25 = 8/75.
No. of days to complete the work: n(8/75) = 1
n = 75/8 = 9.375.
So, it will take 9.375 two day's work, hence 9.375 * 2 = ~19 days.
General Discussion
24 Jun 2017, 06:49
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danlew
Use LCM:
Portion of the work done by Sam is 1/15 = 5/75;
Portion of the work done by Ross is 1/25 = 3/75.
Together in 2*9 = 18 days they'll do (5 + 3)*9 = 72 parts out of 75. On the 19th day Sam will do the remaining job. So, the answer is 19.
Answer: C.
