Question

Ann takes 2 hours to wash her car. When her sister helps her, the job takes 5/4 hours. How long does it take Ann's sister to wash the car by herself.

( Note:I created a table and gave ann a 1/2 fraction and her sister a x/1 fraction but got lost from their.)

Answer 1

Ann's rate ---- 1/2
The job is a constant, let job = 1
Job = rate x time


sister's rate ----- 1/x
combined rate = 1/2 + 1/x = (x+2)/(2x)

1/( (x+2)/2x ) = 5/4
2x/(x+2) = 5/4
8x = 5x+10
3x=10
x=10/3

alone, her sister would take 10/3 hrs or
3 hours and 20 minutes.