SOLUTION: It takes 2 hours and 24 minutes for Gail and Bob to paint a room together. If painting alone, it would take Bob 2 hours more to paint the room than it would take Gail. How long d

Algebra ->  Equations -> SOLUTION: It takes 2 hours and 24 minutes for Gail and Bob to paint a room together. If painting alone, it would take Bob 2 hours more to paint the room than it would take Gail. How long d      Log On


   



Question 143802: It takes 2 hours and 24 minutes for Gail and Bob to paint a room together.
If painting alone, it would take Bob 2 hours more to paint the room than
it would take Gail. How long does it take Gail to paint the room?
Please provide the equation necessary to solve.
I know the answer is 4 hours, but I need to show my work. Thanks!!

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
It takes 2 hours and 24 minutes for Gail and Bob to paint a room together.
If painting alone, it would take Bob 2 hours more to paint the room than
it would take Gail. How long does it take Gail to paint the room?
:
Convert 2 hr 24 min to hrs; 2 + 24/60 = 2.4 hrs
:
Let x = time required for G to paint the room alone
:
It says it takes B two hrs longer to do the job, therefore:
(x+2) = B's time to paint it alone
:
Let the completed job = 1
:
Write an equation representing the fraction painted by each person:
;
2.4%2F%28%28x%2B2%29%29 + 2.4%2Fx = 1
Multiply equation by x(x+2) to eliminate the denominators:
x(x+2)*2.4%2F%28%28x%2B2%29%29 + x(x+2)*2.4%2Fx = x(x+2)(1)
cancel the denominators and you have:
:
2.4x + 2.4(x+2) = x(x+2)
:
2.4x + 2.4x + 4.8 = x^2 + 2x
:
4.8x + 4.8 = x^2 + 2x
:
Arrange as a quadratic equation:
x^2 + 2x - 4.8x - 4.8 = 0
:
x^2 - 2.8x - 4.8 = 0
:
Use the quadratic formula to find the solution:
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
In this equation: a=1; b=-2.8; c=-4.8
x+=+%28-%28-2.8%29+%2B-+sqrt%28-2.8%5E2+-+4+%2A+1+%2A-4.8+%29%29%2F%282%2A1%29+
x+=+%282.8+%2B-+sqrt%287.84+%2B+19.2%29%29%2F%282%29+
You can do the math, the positive solution should be x = 4