SOLUTION: Carpenter A can build a chair in 6 hours while carpenter B can build the same chair in 9 hours. If Carpenter A starts working on a chair for two hours and then carpenter B joins hi

Question 1020353: Carpenter A can build a chair in 6 hours while carpenter B can build the same chair in 9 hours. If Carpenter A starts working on a chair for two hours and then carpenter B joins him, how long will take for the two of them to finish the rest of the job? And. 12/5 hours.
Found 2 solutions by josgarithmetic, josmiceli:
Answer by josgarithmetic(39620) (Show Source): You can put this solution on YOUR website!
RT=J relates work rate, time, amount of job or work. Your example uses 1 for the amount of work of making ONE chair.

The rate for more than one identical working agents acting simultaneously on the same task is the sum of their rates.

Carpenter Rates A B

How long t, for the two of them to finish AFTER carpenter B joins?

Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
What fraction of the job does A
get done in 2 hrs?
-----------------
A's rate of working:
[ 1 chair ] / [ 6 hrs ]

That means 2/3 of the chair remains
to be built
-----------------
B's rate of working:
[ 1 chair ] / [ 9 hrs ]
Let = time in hrs for them to
finish the chair working together
-----------------------------
Add their rates of working to get
rate working together

Multiply both sides by

hrs
------------------
check answer:

OK
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