SOLUTION: blueberry can do a certain job in 10 hours and cheescake can do it in 12 hours. after blueberry and cheesecake have been working together for 1 hour, Duhat joins them, and the thre

Algebra ->  Rate-of-work-word-problems -> SOLUTION: blueberry can do a certain job in 10 hours and cheescake can do it in 12 hours. after blueberry and cheesecake have been working together for 1 hour, Duhat joins them, and the thre      Log On


   

Question 1022905: blueberry can do a certain job in 10 hours and cheescake can do it in 12 hours. after blueberry and cheesecake have been working together for 1 hour, Duhat joins them, and the three completed the job in 3 more hours. How long will it take duhat to do the job alone?
Answer by jorel555(1290) About Me  (Show Source):
You can put this solution on YOUR website!
Let b=blueberry, c=cheesecake, and d=duhat. In one hour, blueberry does 1/10th of the job, and cheese cake does 1/12th of the job. So:
After 1 hour:
1/10+1/12=6/60+5/60=11/60th of the job done.
11/60+3/d+3/10+3/12=1
11d+180+18d+15d=60d
16d=180
d=11.25 hours for Duhat to do the job alone!!!!!!!!!!!