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Anoosh

· started a discussion

· 1 Months ago

How did 60 turn to 160?

Question:
A and B together can complete a work in 15 days, B and C together in 20 days and C and A together     in 30 days. In how many days can C alone complete the work?
Options:
A) 120
B) 130
C) 110
D) 60
E) None of these
Solution:

Ans: (a)

Work done by A and B together in 1 day = 1/15   ………….(1)

Work done by B and C together in 1 day = 1/20   ………….(2)

Work done by C and A together in 1 day = 1/30   ………….(3)

Add Eq. 1, 2 and 3.

Work done by 2(A +B + C) together in 1 day = 1/15 + 1/20 +1/30 = 9/60

Work done by (A + B + C) together in 1 day = 9/120

Work done by C in 1 day =\(\cfrac{9}{120}\) – \(\cfrac{1}{15}\) = \(\cfrac{1}{120}\)

Time taken by C alone = 120 days.

Knowledge Expert

· commented

· 1 Months ago

See the detail solution:

Work done by A and B together in 1 day = 1/15 ………….(1)
Work done by B and C together in 1 day = 1/20 ………….(2)
Work done by C and A together in 1 day = 1/30 ………….(3)
Add Eq. 1, 2 and 3.
Work done by 2(A +B + C) together in 1 day = 1/15 + 1/20 +1/30 = 9/60
Work done by (A + B + C) together in 1 day = 9/120
Work done by C in 1 day =9/120 – 1/15 = 1/120
Time taken by C alone = 120 days.

Knowledge Expert

· commented

· 1 Months ago

Please see the solution very carefully,

Work done by 2(A +B + C) together in 1 day = 1/15 + 1/20 +1/30 = 9/60


Work done by (A + B + C) together in 1 day = (9/60)*(1/2) = 9/120

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