SOLUTION: Find the dimensions of a rectangle whose width is 4 miles less than its length, and whose area is 77 square miles.

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Question 933360: Find the dimensions of a rectangle whose width is 4 miles less than its length, and whose area is 77 square miles.
Answer by LisaDrapeau(7) About Me  (Show Source):
You can put this solution on YOUR website!

Area = Length x Width

Then fill in the equation with what you know:

Area = 77
Length = X (unknown)
Width = X-4 (Width is 4 miles less than Length)

So your equation is:

X * (X-4) = 77
X^2 - 4X - 77 = 0

Then you use the quadratic equation to solve:

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+

where a=1, b=-4, and c=-77

solving for X gives 2 answers, one negative and one positive. The negative one is irrelevant though because you will not have a "less than zero" length.

Your calculator or other online calculators can help solve the equation.

I get X = 11 or -7, and only 11 counts.

To check:

Using the equations at the very top:

Length = 11
Width = 7
Area = 77

Hope that helps :)