SOLUTION: Dave and Edith are working on a science project. It takes them 4 hrs. It would take edith 6 hrs. more than dave if she worked alone. How long would it take for each to finish the

Algebra ->  Rate-of-work-word-problems -> SOLUTION: Dave and Edith are working on a science project. It takes them 4 hrs. It would take edith 6 hrs. more than dave if she worked alone. How long would it take for each to finish the       Log On


   

Question 352569: Dave and Edith are working on a
science project. It takes them 4 hrs. It would take edith 6 hrs. more than dave if she worked alone. How long would it take for each to finish the job if they worked alone?
Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
Dave and Edith are working on a
science project. It takes them 4 hrs. It would take edith 6 hrs. more than dave if she worked alone. How long would it take for each to finish the job if they worked alone?
.
Let x = time it takes for Dave to do it alone
then
x+6 = time it takes for Edith to do it alone
.
4(1/x + 1/(x+6)) = 1
Multiplying both sides by x(x+6) to get rid of denominators:
4((x+6) + x) = x(x+6)
4(2x+6) = x(x+6)
8x+24 = x^2+6x
24 = x^2-2x
0 = x^2-2x-24
0 = (x-6)(x+4)
x = {-4, 6}
Throw out the negative value leaving:
x = 6 hours (Dave's time working alone)
.
Edith:
x+6 = 6+6 = 12 hours