A and B together can complete a work in 12 days. B and C

Solution

ATQ, Let daily work rates of A, B, C be a, b, c. Given: a + b = 1/12 …(1) b + c = 1/15 …(2) a + c = 1/20 …(3) Add all: 2(a + b + c) = 1/12 + 1/15 + 1/20 LCM of 12, 15, 20 is 60. 1/12 = 5/60, 1/15 = 4/60, 1/20 = 3/60 Sum = 12/60 = 1/5 So a + b + c = 1/10 (whole work done in 10 days by all three) Now find b: b = (a + b + c) − (a + c) = 1/10 − 1/20 = (2 − 1)/20 = 1/20 So B’s 1-day work = 1/20 Total daily work = 1/10 Share of B in work = (1/20) ÷ (1/10) = 1/2 So B’s share of Rs 7,200 = 1/2 × 7200 = Rs 3,600