Question

One printing machine works twice as fast as another. When both machines are used, they can print a magazine in 3 hours. How many hours would each machine require to do the same job alone?
this is how I attempted to do the problem, but I don't know exactly how I figured it out and what I solved. http://www.slimber.com/index.php?image=math-problem.g149917

Answer 1

do you plug in the x = 9 into the box thingy and then you know how long each machine takes alone to do the job?

Answer 2

hello?

Answer 3

I think I kinda got it, machine 1 is 2/9 and machine 2 is 1/9, but how exactly do I convert that to hours?

Answer 4

x= hours for 1 machine to do the job
2x = hours for other machine to do the job.
1/x = part of job done in 1 hour by first machine
1/2x = part of job done in 1 hour by second machine
3/x= part of job done by first machine in 3 hours
3/2x = part of job done by second machine in 3 hours
Together they do 1 entire job
\[\frac{3}{x}+\frac{3}{2x}=1\]

Answer 5

\[\frac{6}{2x}+\frac{3}{2x}=1\]
\[\frac{9}{2x}=1\]
\[2x=9\]

Answer 6

\[x=4.5\]

Answer 7

So it takes the first machine 4.5 hours to do the job by itself and the second machine requires 9 hours to so the job by itself.

Answer 8

sorry got stuck on the first part, when you multiplied the 2 by the 1/x, why did the 2 go to the bottom? shouldn't it be 3(2/x)? because the 2 becomes 2/1, and the 2 is on the top, so it should be 2/x? and then the 3, it would be 6/x?

and also, how did you get 6/2x?

Answer 9

If it takes you 5 hours to mow your lawn you can mow 1/5 of the lawn in 1 hour and in three hours you mow 3 times 1/5
If it takes your sister twice as long to mow the lawn, she can mow it is 2(5) hours and in three hours she can mow 3 times 1/2(5)

Answer 10

wat. ?

Answer 11

And I got 6/2x because
\[\frac{3}{x}\times \frac{2}{2}=\frac{6}{2x}\]

Answer 12

oh okay :D thanks

Answer 13

x= hours for 1 machine to do the job
2x = hours for other machine to do the job.
1/x = part of job done in 1 hour by first machine
1/(2x) = part of job done in 1 hour by second machine
3/x= part of job done by first machine in 3 hours
3/(2x) = part of job done by second machine in 3 hours