Question

54. If A can do as much work in 4 hours as B can do
in 6 hours, or as C can do in 8 hours, how long
will it take C to complete a piece of work, one-
third of which has been done by A working 8
hours and B working 18 hours?
(a) 60 hours
(6) 70 hours
(c) 80 hours
(d) 90 hours​

Answer 1

we know efficiencies of A B C is 6,4,3 respectively

A work for 8 hrs = 8 * 6 = 48

B work for 18 hrs = 18 * 4 = 72

work completed by A and B = 48+72 = 120

120 is 1/3 of work

Total work = 360.... (A and B completed 120)

Remaining 240 work to be completed by C

Time take = 240/3 = 80 hr

ANSWER : 80 hours