A & B can do a work in 72 days, B & C can do it in 120 days, A and C can do it in 90 days. A alone can do it in?
Solution
Correct Answer: Option B
(A + B)' s 1 day's work = 1/72
(B + C)' s 1 day's work = 1/120
(A + C)'s 1 day's work = 1/90
Adding, we get, 2 (A + B + C)'s 1 days
work = (1/72 + 1/120 + 1/90)
= 12/360
= 1/30
(A + B + C)'s 1 day's work = 1/60
A's 1 day's work = (1/60) - (1/120)
∴ A alone can finish the work in 120 days.
(B + C)' s 1 day's work = 1/120
(A + C)'s 1 day's work = 1/90
Adding, we get, 2 (A + B + C)'s 1 days
work = (1/72 + 1/120 + 1/90)
= 12/360
= 1/30
(A + B + C)'s 1 day's work = 1/60
A's 1 day's work = (1/60) - (1/120)
∴ A alone can finish the work in 120 days.
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