Question

16) Working alone, it takes LeeAnn 30 minutes to clean the backyard. Mandy can clean the

backyard in 25 minutes. If they worked together, how long would it take them to clean the yard?
Round to the nearest minute.

Answer 1

Explanation:

Work done is transfer of energy...... but without complicating things a little further let's just consider the amount of work done while cleaning the backyard is the same regardless of who the doer is/ how many in number are the doers. So

So power is the time rate change of work done:

`P=w/t\\`

let's say power of LeeAnn =L, Mandy=M

`L=w/30 minutes\\M=w/25 minutes\\`

And if they worked together their power will add up to L+M

`L+M=w/T\\`, while T is the amount of time needed when they clean together.

`L+M=w/T\\w/30min + w/25min =w/T\\1/30min+1/25min=1/T, w\\eq 0\\1+(6/5)=30/T\\11/5=30/T\\11T=150\\T=150/11 min\\T=13.6 min`