math question

[ak47]

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These kinds of questions keep coming up. Anyone have an easy way to do this?

Justin requires 5 hours to pair a certain room. Suzanne requires 3 hours to paint the same room. If Justin and Suzanne work together but separately, how long will it take to paint 1/3 of the room?

Answer: 5/8 hour (highlight me)

Thanks

 

[bumpski20]

the equation you use for combining rates is (A*B)/(A+B) where A is one rate and B is the other. for this case it would be (5*3)/(5+3) which equals 15/8. this would be how long it would take to paint the whole room but since its only 1/3 multiply 15/8 by 1/3 and you get 5/8