A in 50 hrs
B in 60 hrs
C in 75 hrs
Let total work to be completed be 300 units (took 300 as it is the LCM of all three)
Efficiency-
A does 6 units of work in 1 hr
B does 5 units of work in 1 hr
C does 4 units of work in 1 hr
Total units of work in 1 hr = 15
Total units of work to be done = 300
Total time taken if all three work together = 300/15 = 20 hrs
In the first 10 hrs, half of the work is done,
that is, 150 units of work is done in 10 hrs.
after 10 hrs,
only B and C work.
B stops BEFORE 15 HOURS FROM COMPLETION, that means C works alone in the last 15 hrs.
C does 4 units of work in 1 hr, so,
in 15 hrs, C does 60 units of work.
Remaining work = 150-60 = 90
This much work would be done by B and C together.
B and C in 1 hr does 9 units of work.
So 90 units will be complete in 10 hrs.
Therefore, total time taken for completion = 10 + 10 + 15 = 35 hrs
FINAL ANSWER - Option C
Bunuel
12 Days of Christmas 2024 - 2025 Competition with $40,000 of PrizesIn a factory, Machine A, working alone, can complete a task in 50 hours, Machine B, working alone, can complete the same task in 60 hours, and Machine C, working alone, can complete it in 75 hours. All three machines started working together on the task. However, Machine A stopped working after 10 hours, and Machine B stopped 15 hours before the task was completed. How many total hours were required to finish the task?
A. 25
B. 30
C. 35
D. 40
E. 45