Machine A can do a certain job in 8 hours.
Machine A can do a certain job in 8 hours. Machine B can do the same job in 10 hours. Machine C can do the same job in 12 hours. All three machines start the job at 9:00 a.m. Machine A breaks down at 11:00 a.m., and the other two machines finish the job. Approximately what W time will the job be finished?
Answer/Solution
1:00 p.m.
Steps/Work
Ans: C (1:00pm)
From 9:00-11:00c(2 hrs)
A can do 1/8 Job/hr. so in 2 hours he can do 1/4 job.
B can do 1/10 job/hr so in 2 hrs. he can do 1/5 Job.
C can do 1/12 job/hr so in 2 hours he can do 1/6 job.
Total = 1/4+1/5+1/6 = 37/60 Job
Now balance work needs to be done by B and C.
Balance Work= 23/60 Job
Combined rate of B and C = 1/10+1/12 = 11/60 job/hr.
So they will do 22/60 work in 2 hrs (approx. to the balance work of 23/60)
Hence the Job will be completed 2hrs. after 11:00 i.e. @ 1:00pm=W
Ans: C (1:00pm)
From 9:00-11:00c(2 hrs)
A can do 1/8 Job/hr. so in 2 hours he can do 1/4 job.
B can do 1/10 job/hr so in 2 hrs. he can do 1/5 Job.
C can do 1/12 job/hr so in 2 hours he can do 1/6 job.
Total = 1/4+1/5+1/6 = 37/60 Job
Now balance work needs to be done by B and C.
Balance Work= 23/60 Job
Combined rate of B and C = 1/10+1/12 = 11/60 job/hr.
So they will do 22/60 work in 2 hrs (approx. to the balance work of 23/60)
Hence the Job will be completed 2hrs. after 11:00 i.e. @ 1:00pm=W
Ans: C (1:00pm)