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 time R will the job be finished?  Choose the correct choice from the following choices
A) Noon
B) 12:30 p.m.
C) 1:00 p.m.
D) 1:30 p.m.
E) 2:00 p.m.
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=R   Ans: 1:00 p.m. (1:00pm)
<result>C</result>
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 time R will the job be finished?