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Mathematics 10 Online
klmjnmkj:

math problem

klmjnmkj:

@AZ

klmjnmkj:

1 attachment
AZ:

this is a very interesting question hmmm

AZ:

And we can't use calculus either so let's dumb it down |dw:1617828915139:dw| what is the perimeter? add up all the letters that you see

thony:

wouldnt it just be 1 x on either side bc it's 4 walls? and not 6

AZ:

the perimeter = 234 and we also know that the area is length * width and we have two rectangles here so 2 * length *width the length is x and the width is y so area = 2 * x * y and we want to get the maximum area but we can proceed once you determine what the formula for perimeter is

surjithayer:

let x be the length and y be the width. 234=2x+3y 3y=234-2x \[y=\frac{234-2x}{3}\] \[area A=x*y=x(\frac{234-2x}{3})\] \[A=\frac{1}{3}(234 x-2x^2)\] \[\frac{dA}{dx}=78-\frac{4x}{3}\] \[\frac{dA}{dx}=0~gives~4x=234\] x=117/2 \[\frac{d^2A}{dx^2}=-\frac{4}{3}\] \[\frac{d^2A}{dx^2} <0~at~x=117/2\] so A is maximum if x=117/2 3y=234-2 *117/2=234-117=117\] y=117/3=39 so with the given condition length=117/2=58.5 ft width =39 ft

klmjnmkj:

thanks

surjithayer:

yw

AZ:

Hmm, yeah that is correct. I could have just made the entire length as 'x' instead of breaking it up like I did in my drawing

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