SunthoshiTejaswi wrote:
Bunuel wrote:
Machine A and machine B process the same work at different rates. Machine C processes work as fast as Machines A & B combined. Machine D processes work three times as fast as Machine C; . Assume all four machines work at fixed unchanging rates. If Machine A works alone on a job, it takes 5 hours and 40 minutes. If all four machines work together on the same job simultaneously, how long will it take all of them to complete it?
A. 8 minutes
B. 17 minutes
C. 35 minutes
D. 1 hour and 15 minutes
E. 1 hours and 35 minutes
Kudos for a correct solution.
hi bunnuel can you please explain the same with rate of a taken as 1/a
then am getting 3b=a
Machine A processes work in 5 hours 40 mins = 5x60 + 40 = 340 Mins
i.e. Machine A processes in 1 mins = 1/340 work
Let Machine B processes in 1 min = 1/b work
i.e. The Work of Machine C in 1 Min = Work of A and B together in 1 min = (1/340)+(1/b)
i.e. The Work of Machine D in 1 Min = 3*Work of C in 1 min = 3*[(1/340)+(1/b)]
But, Machine D’s work rate is also exactly four times Machine B’s rate
i.e. The Work of Machine D in 1 Min = 4* (1/b) = 3*[(1/340)+(1/b)]
i.e. 4/b = 3*[(b+340)/340*b]
i.e. (4/b) * (340*b) = 3b + 1020
i.e. 1360 = 3b + 1020
i.e. b = 340/3i.e. B's 1 Min work = 3/340
i.e. C's 1 Min work = (3/340)+(1/340) = 4/340
i.e. D's 1 Min work = 3*(4/340) = 12/340
Work of A, B, C and D combined in 1 min = (1/340) + (3/340) + (4/340) + (12/340) = (20/340)
i.e. Time taken by A, B, C and D working together = 340/20 mins = 17 mins
Answer: option
P.S.
Your Mistake is you are getting 3b = a whereas the CORRECT relation is b=3a