2 people together can paint a room in 5 hours. it takes one of them 9 hours to paint the room how long would it take the other friend to paint by himself?

Question

Its a precalculus question in rational espressions

Answer 1

The first person does 1/9 parts per hour.

The 2nd person does 1/x parts per hour

The sum of how much they do per hour, multiplied by 5 equals 100% or 1

 

5(1/9 + 1/x) = 1

1/9 + 1/x = 1/5

1/x = 1/5 - 1/9

1/x = 9/45 = 5/45

1/x = 4/45

4x = 45

 

x = 45/4 = 11 1/4 hours for the other friend to do it alone