Gray's rate = 1/15
Anna' rate = 1/20
Job done by Gray = 6(1/15) = 2/5
leaving 3/5 of the job left to be done by Anna
time for Anna to complete
= (3/5) / (1/20)
= 12
It will take her 12 days to finish the roof
Gray Glaze requires 15 hours to put a new roof on a house. His apprentice, Anna Gandy, can record the house by herself in 20 hours. After working alone on a roof for 6 hours, Gary leaves for another job. Anna takes over and completes the job. How long does it take Anna to complete the job?
1 answer