Question

Andrea can clean a house 4 times as fast as Denise. When they work together, Andrea and Denise can clean a large house in 8 hours. How many hours would it take Denise to clean the house by herself?

20

15

10

5

Answer 1

15

Answer 2

How do you know? @ariyanamckeown

Answer 3

let x = Denise's time if do by herself
4x = Andrea's time if do by herself

the time when they work together can be writtten as
(4x * x)/(4x + x) = 8

4x^2/5x = 8
4x/5 = 8
4x = 5 * 8
4x = 40
x = 10

so, Denise's time id work by herself is 10 hours

Answer 4

* if

Answer 5

(A + D)8 = 1
A = 4D

so,
(4D + D)8 = 1
5D = 1/8
D = 1/40

so, it would take Denise 40 hours. The right answer is not on the list, unless you meant to ask for the hours it takes Andrea to clean the house