SOLUTION: A dairy is required to have a waste holding pond for runoff. Tom plans to build a pond that will be 20 ft by 15 ft. there will be a border of equal length around the pond. the tota

Question 332700: A dairy is required to have a waste holding pond for runoff. Tom plans to build a pond that will be 20 ft by 15 ft. there will be a border of equal length around the pond. the total area of the pond and the border is 500ft. How wide will the border be?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
the pond is 20 by 15
..
let the border width be x
..
so the width including border will be 15+2x ( x on either side)
The length including width = 20+2x
..
Area of entire plot including border = 500 sq.ft= (15+2x)(20+2x)
..
4x^2+70x+300=500
4x^2+70x-200=0
4x^2+80x-10x-200=0
4x(x+20)-10(x+20)=0
(x+20)(4x-10)=0
4x-10=0
4x=10
x=10/4
x= 2.5 feet.
..
CHECK
(15+5)*(20+5)= 500
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