Question

Dirk can clean a playground in 5 hours. Geralyn can clean a playground in only 4 hours.

Which of the following can be used to determine the amount of time it would take for Dirk and Geralyn to clean a playground together?

a. 1 over 5 plus 1 over x equals 1 over 4
b. 1 over x plus 1 over 4 equals 1 over 5
c. 1 over 5 plus 1 over 4 equals 1 over x
d. 1 over 4 plus 1 over 5 equals x over 9

Answer 1

Hint:


x = time it takes Dirk to do the job alone
y = time it takes Geralyn to do the job alone
z = time it takes for them to do the job working together


\[\Large \frac{1}{x}+\frac{1}{y}=\frac{1}{z}\]

Answer 2

@jim_thompson5910 thank you so so much!

Answer 3

you're welcome