SOLUTION: "A mother can rake a yard in 90 minutes and her daughter can do it in 60 minutes.If the mother rakes for 15 minutes before her daughter joins her,how long will it take them to fin

Algebra ->  Rate-of-work-word-problems -> SOLUTION: "A mother can rake a yard in 90 minutes and her daughter can do it in 60 minutes.If the mother rakes for 15 minutes before her daughter joins her,how long will it take them to fin      Log On


   

Question 935161: "A mother can rake a yard in 90 minutes and her daughter can do it in 60 minutes.If the mother rakes for 15 minutes before her daughter joins her,how long will it take them to finish the work?"
Answer by josgarithmetic(39616) About Me  (Show Source):
You can put this solution on YOUR website!
Mother rate, 1/90 yards per minute.
Daughter rate, 1/60 yards per minute.
t, time for combined Mother and Daughter raking together, to finish...

%281%2F90%29%2A15%2B%281%2F90%2B1%2F60%29%2At=1, for ONE JOB.

LCD is 2%2A2%2A3%2A3%2A5.

2%2A15%2B%282%2B3%29t=180
30%2B5t=180
5t=150
highlight%28t=30%29, MINUTES together to finish after Mother works for 15 minutes alone.