SOLUTION: A rectangular countertop has an area of 15 ft^2. If the width is 3.5 shorter than the length, what are the dimensions of the countertop?

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Question 1087935: A rectangular countertop has an area of 15 ft^2. If the width is 3.5 shorter than the length, what are the dimensions of the countertop?
Answer by ikleyn(52790) About Me  (Show Source):
You can put this solution on YOUR website!
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Answer. 6 and 2.5 ft. 

To solve it MENTALLY, consider rectangle with doubled dimensions.

Then the area is 15*4 = 60 ft^2, and the difference L - W = 7 ft.


Now find (MENTALLY) two factors of 60 that differ in 7 (=2*3.5) ft.


They are 12 and 5.


Now divide 12 and 5 by 2 to return to the original dimensions.


You will get 6 and 2.5.

Solved (MENTALLY).


The alternative way is to solve a quadratic equation with decimal coefficients.