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41 votes
41 votes
Mary can do a job in 80 minutes, Working with Jané, both can do the job in 30

minutes. How long will it take Jane to do the job alone?

User Kevin Jose
by
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1 Answer

6 votes
6 votes

Answer:

see below

Explanation:

The equation to determine the work time is

1/a+1/b = 1/c where a and b are the times alone and c is the time together

1/80 + 1/30 = 1/c

Multiply by the least common denominator to clear the fractions, which is 240c

240c(1/80 + 1/30 = 1/c)

3c+8c = 240

11c = 240

Divide by 11

11c/11 =240/11

c = 240/11 minutes

c=21.81818

Approximately 22 minutes

User Neb
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