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- Dec 20th 2009, 07:56 AM #1

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- Dec 2009
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## Lawnmower Problem

The Smith family has two lawnmowers, one old and one new. Here is a table for how long it takes each son to mow the lawn using each lawnmower and working alone.

New Old

Johnny 2 hrs 2 hrs 30 min

Jimmy 3 hrs 3 hrs 40 min

How long does it take them working together:

a. If Johnny uses the new one and Jimmy uses the old one?

b. If Johnny uses the old one and Jimmy uses the new one?

PLEASE HELP

Thanks,

Steve

- Dec 20th 2009, 10:08 AM #2

- Dec 20th 2009, 10:13 AM #3

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- Lexington, MA (USA)
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Hello, Steve!

The Smith family has two lawnmowers, one old and one new.

Here is a table for how long it takes each son to mow the lawn using each lawnmower and working alone.

How long does it take them working together:

(a) If Johnny uses the new one and Jimmy uses the old one?

(b) If Johnny uses the old one and Jimmy uses the new one?

(a) Using the new mower, Johnny takes mows the lawn in 2 hours

. . In one hour, he mows of the lawn.

. . In hours, he mows of the lawn.

Using the old mower, Jimmy takes hours.

. . In one hour, he mows of the lawn.

. . In hours, he mows of the lawn.

Working together, in hours, they can mow: . of the lawn.

But in hours, we expect to mow the entire lawn (1 lawn).

There is our equation: .

Working together, they can mow the law in hours.

Use the same procedure for part (b).