SOLUTION: art can do a job in 30 minutes bob can do it in 40 min. and carl can do it in 60 min , how long will it take them all to do the job if they help eachother, write the equation

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Question 172783: art can do a job in 30 minutes bob can do it in 40 min. and carl can do it in 60 min , how long will it take them all to do the job if they help eachother, write the equation
Found 2 solutions by vleith, Mathtut:
Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
Art can do 1/30 job/minute
Bob can do 1/40
Carl can d0 1/60
How many minutes will it take to for the 3 of them to do a single job?
1+=+m%281%2F30+%2B+1%2F40+%2B+1%2F60%29
1+=+m%284%2F120+%2B+3%2F120+%2B+2%2F120%29
1+=+m%289%2F120%29
120%2F9+=+m+
13.333 minutes

Answer by Mathtut(3670) About Me  (Show Source):
You can put this solution on YOUR website!
art can do 1/30 job per minute
:
bob.......1/40 job per minute
:
carl.......1/60 job per minute
those are all rates.....lets call time=t
:
t/30+t/40+t/60=1(job)
:
4t+3t+2t=120...muliply each term by 120
:
9t=120
:
highlight%28t=120%2F9=40%2F3%29or 13 and 1/3 minutes to do the entire job...