SOLUTION: Mark can harvest the crops in 9 days. His father needs 15 hours to complete the same task. If Mark works on the first day, his father works on the second day, Marks works again on

Algebra ->  Equations -> SOLUTION: Mark can harvest the crops in 9 days. His father needs 15 hours to complete the same task. If Mark works on the first day, his father works on the second day, Marks works again on       Log On


   

Question 1077473: Mark can harvest the crops in 9 days. His father needs 15 hours to complete the same task. If Mark works on the first day, his father works on the second day, Marks works again on the third day, his father works on the fourth day, and so on, how many days does it take to harvest 4/5 of the crops?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
This would make sense if this read:
Mark can harvest the crops in 9 days.
His father needs 15 "days" to complete the same task.
If Mark works on the first day, his father works on the second day, Marks works again on the third day, his father works on the fourth day, and so on, how many days does it take to harvest 4/5 of the crops?
:
let the completed job = 1
let d = no. days to accomplish this
d%2F2(1%2F9 + 1%2F15) = 4%2F5
d%2F18 + d%2F30) = 4%2F5
multiply by 90 to cancel the denominators
5d + 3d = 18(4)
8d = 72
d = 72/8
d = 9 days to do 4/5 of the job
:
See how that comes out
1%2F9+%2B+1%2F15+%2B+1%2F9+%2B+1%2F15+%2B+1%2F9+%2B+1%2F15+%2B+1%2F9+%2B+1%2F15+%2B+1%2F9 = 5%2F9+%2B+4%2F15 = .822 which is very close to 4/5 of the job