Jonathan can type a 20 page document in 40 minutes, Susan can type it in 30 minutes, and Jack can type it in 24 minutes. Working together, how much time will it take them to type the same document?

I believe the way you would solve this problem is by finding a common denominator. Once you find your common denominator you will add the top numbers together then divide to come up with you answer.

- stapel_eliz
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To learn, in general, how to set up and solve this sort of word problem, tryJonathan can type a 20 page document in 40 minutes, Susan can type it in 30 minutes, and Jack can type it in 24 minutes. Working together, how much time will it take them to type the same document?

Then, following the instructions outlined there, convert the times to rates:

. .. .time to complete job (minutes):

. . . . .Jon: 40

. . . . .Sue: 30

. . . . .Jack: 24

. . .completed per time unit (minute):

. . . . .Jon: 1/40

. . . . .Sue: 1/30

. . . . .Jack: 1/24

Then how much do they complete, together, in one minute?

Then how many minutes will they need, if working together, to complete the task?