SOLUTION: The area of a grassy plot is 480 metres. If each side had been 5m longer, the area would have been increased by 245 square metres. Find the length of the fence to surround it.

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Question 560291: The area of a grassy plot is 480 metres. If each side had been 5m longer, the area would have been increased by 245 square metres. Find the length of the fence to surround it.
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
let the length be x
width = y
xy=480
x=480/y
(x+5)(y+5) is the area after increasing the sides
xy+5x+5y+25
xy+5x+5y+25- xy = 245
5x+5y=245-25
5x+5y=225
x+y=45
480/y +y = 45
multiply equation by y
480 +y^2=45y
y^2-45y+480=0
Find the roots of the equation by quadratic formula

a= 1 , b= -45 , c= 480

b^2-4ac= 2025 + -1920
b^2-4ac= 105
%09sqrt%28%09105%09%29=%0910.25%09
x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=%28-b%2Bsqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=( 45 + 10.25 )/ 2
x1= 27.62
x2=( 45 -10.25 ) / 2
x2= 17.38
sides are 27.62 & 17.38m

The Perimeter=2*( 27.62 + 17.38)
= 90 meters