AFCAT Model Paper 7

Given: A, B and C can do a piece of work in 24, 20 and 40 days respectively C left the work 4 days before the completion of the work Calculation: Speed of A = work to do / time it takes to do the work $= \frac{1}{24}$ Speed of B = work to do / time it takes to do work $= \frac{1}{20}$ Speed of C $= \frac{1}{40}$. When they work together they take t days to complete the work with the given condition. So according to equation: ⇒ Work done by $A = \frac{t}{24}$ ⇒ Work done by $B = \frac{t}{20}$ ⇒ Work done by $C = \frac{t-4}{40}$ So, According to the question $\frac{t}{24} + \frac{t}{20} + \frac{t-4}{40} = 1$ ∴ Time taken t = 9.43 days.