Posted by Kelly on Saturday, January 21, 2012 at 2:52am.
Adam has a hockey rink in his backyard. The current dimensions are 10m by 20m. Adam wants to have a hockey tournament and needs to double the area of his hockey rink. How much must Adam increase each dimension if he wants to increase them the same amount?

Math, Quadratics  Mac, Saturday, January 21, 2012 at 4:00am
Current area = 200m2 [10m x 20m]
New area = 400m2 [10y x 20y]
So, 400 = 200y2
So, y2= 2
So, y = 1.41
So, each side must be increased by a factor 0f 1.41 times.
I this correct or do they mean add the same length to each side?

Math, Quadratics  Damon, Saturday, January 21, 2012 at 5:36am
same to each
(10+x)(20+x) = 400
200 + 30 x + x^2 = 400
x^2 + 30 x  200 = 0
x = [ 30 +/ sqrt(900 + 800) ]/2
x = [ 30 +/ 10 sqrt 17 ] /2
x = 15 +/ 5 sqrt 17
x = 5.62
new dimensions
15.62 * 25.62 = 400 ok

Math, Quadratics  Kelly, Saturday, January 21, 2012 at 8:09am
Hi Damon, I got the same answer as you up to the equation x^2 + 30x  200=0, but after that I don't understand what happened after that.. where does the 900 and 800 come form? and why you do divide by 2? thanks
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