SOLUTION: Twin brothers, Billy and Bobby, can mow their grandparent's lawn together in 96 minutes. Billy could mow the lawn by himself in 20 minutes less time that it would take B
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Question 1174767: Twin brothers, Billy and Bobby, can mow their grandparent's lawn together in 96 minutes. Billy could mow the lawn by himself in 20 minutes less time that it would take Bobby. How long would it take Bobby to mow the lawn by himself?
Answer by VFBundy(438) (Show Source): You can put this solution on YOUR website!
Bobby's rate of work = of the lawn per minute
Billy's rate of work = of the lawn per minute
Rate of work working together = + of the lawn per minute = of the lawn per minute
Solve for x:
+ =
+ =
=
=
Cross-multiply:
=
=
=
=
Use the quadratic formula to solve for x:
x = = 9.48
x = = 202.52
There are two solutions. Because Billy's rate of work is of the lawn per minute, that means the first solution, x = 9.48, would make Billy's rate of work . This is a negative rate and, therefore, impossible. This means we can eliminate this solution.
We are left with the solution, x = 202.52. We are looking for how long it would take Bobby to mow the lawn himself. Bobby's rate of work is of the lawn per minute. Plugging in x = 202.52, Bobby's rate of work is of the lawn per minute. That means it would take Bobby 202.52 minutes to mow the lawn himself.
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