math
posted by kelsey .
Ryan takes 12 minutes to rake up and bag a pile of leaves. His sister Kareesa takes twice as long. How many minutes would it take both of them working together to complete 10 bags of leaves

Ryan's rate per bag = 1/12
sister's rate ber bag = 1/24
combined rate = 1/12 + 1/24 = 3/24
time per bag working together = 1/(3/24) = 24/3 = 8 minutes
so it would take them 80 minutes to do 10 bags