SOLUTION: If A does a job in 16 hours and B does the same job in 12 hours, if B and C do the job together in 4 hours how long would it take C to do the job himeself

Algebra ->  Rate-of-work-word-problems -> SOLUTION: If A does a job in 16 hours and B does the same job in 12 hours, if B and C do the job together in 4 hours how long would it take C to do the job himeself      Log On


   

Question 905102: If A does a job in 16 hours and B does the same job in 12 hours, if B and C do the job together in 4 hours how long would it take C to do the job himeself
Found 2 solutions by josmiceli, richwmiller:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
B and C together:
+1%2F12+%2B+1%2Ft%5Bc%5D+=+1%2F4+
Multiply both sides by +12t%5Bc%5D+
+t%5Bc%5D+%2B+12+=+3t%5Bc%5D+
+2t%5Bc%5D+=+12+
+t%5Bc%5D+=+6+
It takes C 6 hrs to do the job alone

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
1/b+1/c=1/4
1/12+1/c=1/4
rate for A alone 12
rate for A & c together 4
1/a+1/c=1/x
1/12+1/c=1/4
1/c=1/4-1/12
1/c=12/48-4/48
1/c=8/48
1/c=1/6
c=6
rate for c alone 6
check
1/12+1/6=1/4
6/72+12/72=1/4
18/72=1/4
ok

Note we have extra info. We don't need the info about A unless you left something out