Step-by-step explanation:
The area of any 2-d quadrilateral is equal to the base of the shape times the height, though we can just sub in length and width here. The key bits of information here is the aspect ratio (4:3) and the given area (300 in^2).
So far this gives us L∗W=300in2
Now, the aspect ratio given implies for every 4 inches in length, there will be 3 inches in width. This allows us to factor out a 4 and a 3 from the Length and Width respectively and give them the same constant variable, like so:
4x∗3x=300in2
Now, some might be tempted to go ahead with 12x here, but let’s expand the left side out to see what’s really going on:
4∗x∗3∗x=300in2
From here, let’s resolve like terms Our constants will multiply together and give us 12, and x * x of course gives us x^2 to give us the following:
12x2=300in2
From here, simply divide through by 12 to isolate x on one side,x2=25
And finally take the square root of both sides to work out what your common factor is,
x=5
Now that we have out common factor, let’s plug it back into our original formula to find our Length and Width, like so.
(4∗5)in∗(3∗5)in=300in2
20in∗15in=300in2
Therefore, the Length of our rectangle is 20in, and the Width of our rectangle is 15in
. Our derivative, then, is 
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