Question

A group of college students is volunteering for Help the Homeless during their spring break. They are putting the finishing touches on a house they built. Working alone, Irina can paint a certain room in 9 hours. Paulo can paint the same room in 8 hours. Write an equation that can be used to find how long it will take them working together to paint the room. How many hours will it take them to paint the room? If necessary, round your answer to the nearest hundredth.

A.
`(x)/(9) + (x)/(8) = 1`; 2.18 hours
B.
`(1)/(9) + (1)/(8) = (1)/(x)`; 3.73 hours
C.
`(9)/(x) + (8)/(x) = 1`; 8.5 hours
D.
`(x)/(9) + (x)/(8) = 1`; 4.24 hours

Answer 1

D 4.24

Explanation:

Assume the area of room be A

Irina painting speed be x, 8x = A

Paulo painting speed be y, 9y = A

Together painting speed = x + y = A/8 + A/9

Assume together painting time = t

(A/8 + A/9) t = A

(1/8 + 1/9)t = 1

17t = 72

t = 4.24