SOLUTION: a small coputer can process marketing data in 30 hours. to speed up processing anoher can do same work in 12 hours. how long if both work together

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Question 1150249: a small coputer can process marketing data in 30 hours. to speed up processing anoher can do same work in 12 hours. how long if both work together
Found 2 solutions by ikleyn, greenestamps:
Answer by ikleyn(52841) About Me  (Show Source):
You can put this solution on YOUR website!
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First comp does  1%2F30  of the job per hour.


Second comp does  1%2F12  of the job per hour.


Working together, both comps do  1%2F30 + 1%2F12 = 2%2F60+%2B+5%2F60 = 7%2F60  of the job per hour.


Hence, these two comps will complete the job in  60%2F7 hours  = 84%2F7 hours working together.    ANSWER

Solved,  answered,  explained and completed.

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If you want more entertainments  (I mean if you want to see other similar solved problems),  then look into the lessons
    - Using Fractions to solve word problems on joint work
    - Solving more complicated word problems on joint work
    - Selected joint-work word problems from the archive
in this site.

Read them and get be trained in solving joint-work problems.

Also,  you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this textbook under the topic
"Rate of work and joint work problems"  of the section  "Word problems".


Save the link to this online textbook together with its description

Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson

to your archive and use it when it is needed.


Answer by greenestamps(13203) About Me  (Show Source):
You can put this solution on YOUR website!


Here is an alternative to the standard algebraic method for solving "working together" problems like this, as shown by the other tutor.

Consider the least common multiple of the two given times. One computer can do the job in 30 hours; the other in 12 hours.

The LCM of 30 and 12 is 60. In 60 hours, the first computer could do the job 60/30 = 2 times; the other could do it 60/12 = 5 times.

So in 60 hours the two computers together could do the job 7 times; that means the amount of time it takes them to do the one job is 60/7 hours.

And for a student competing in timed math competitions, where only an answer is needed, without any formal solution method, the answer to any question like this involving two workers working together is (a*b)/(a+b), where a and be are the amounts of time required for the two workers individually.

In this problem, that is

%2812%2A5%29%2F%2812%2B5%29+=+60%2F7