SOLUTION: There are two machines that produce aluminum cans. The newer machine can produce 7200 cans in 200 minutes. It takes the older machine 300 minutes to produce that many cans. If the

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: There are two machines that produce aluminum cans. The newer machine can produce 7200 cans in 200 minutes. It takes the older machine 300 minutes to produce that many cans. If the       Log On


   

Question 1143494: There are two machines that produce aluminum cans. The newer machine can produce 7200 cans in 200 minutes. It takes the older machine 300 minutes to produce that many cans. If the two machines work together, how long will it take them to produce 7200 cans?
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39630) About Me  (Show Source):
You can put this solution on YOUR website!
7200 cans, same as 1 job.

1%2F200%2B1%2F300=1%2FT

T=1%2F%281%2F200%2B1%2F300%29

Answer by ikleyn(52898) About Me  (Show Source):
You can put this solution on YOUR website!
.

Newer machine produces  7200%2F200 = 36 cans per minute.


The older machine produces  7200%2F300 = 24 cans per minute.


Working together, the two machines produce  36 + 24 = 60 cans per minute.


Working together, the two machines will produce 7200 cans in  7200%2F60 = 120 minutes = 2 hours.    ANSWER

It is  VERY  SIMPLE  and  SIMPLEST  joint work problem for 4-grade students,  and there is no any need
to use three-level fractions to solve it,  as  @josgarithmetic tries to teach you.

All you need to do is to divide integer numbers to find rate of work of each machine;
then add rates to find combined rate of work of two machines working together;
and,  finally,  to divide the total production volume to this combined rate of work.

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If you want to see other similar solved problems and to wider your knowledge, look into the lesson
    - Special joint work problems that admit and require an alternative solution method
in this site.