Rational Word Problems

[Geeger]

I dont know how to even set this problem up much less solve for it and i have a test in two days

If one person takes 3 hours to do a job and another person takes 4 hours to do the same job, why is 3.6 hours not a valid answer to the problem “How long will it take for them to do the job working together?”

 

[Deleted member 4993]

I dont know how to even set this problem up much less solve for it and i have a test in two days

If one person takes 3 hours to do a job and another person takes 4 hours to do the same job, why is 3.6 hours not a valid answer to the problem “How long will it take for them to do the job working together?”

If one person (A) takes 3 hours to do a job → in one hour what fraction of the job can A complete?

If one person (B) takes 4 hours to do a job → in one hour what fraction of the job can B complete?

Working together - what fraction of the job (A+B) can complete in one hour → Working together - how long will (A+B) take to finish the job

Now you can determine the reason for " why is 3.6 hours not a valid answer ".....