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A rectangular circuit board is designed to have a width of W inches, a length of L inches, a perimeter of P inches, and an area of A square inches. Which of the following equations must be true?

A) 2W^2 + PW + 2A = 0
B) 2W^2 − PW + 2A = 0
C) 2W^2 − PW − 2A = 0
D) W^2 + PW + A = 0
E) W^2 − PW + 2A = 0



Perimeter of the circuit board , \(P = 2W + 2L\)

As all the answer choices are in terms of A, P and W, let us express L in terms of P and W

\(L = \frac{P}{2} - W\)

Substituting the above value of L in equation \(2A = 2*W*L\),

\(2A = 2*(W*L) = 2* W *( \frac{P}{2}-W)\)

Or, \(2A = WP - 2W^2\)

Or, \(2W^2 -WP+2A =0\)

Answer: B
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A rectangular circuit board is designed to have a width of W inches, a length of L inches, a perimeter of P inches, and an area of A square inches. Which of the following equations must be true?

A) 2W^2 + PW + 2A = 0
B) 2W^2 − PW + 2A = 0
C) 2W^2 − PW − 2A = 0
D) W^2 + PW + A = 0
E) W^2 − PW + 2A = 0



Perimeter of the circuit board , \(P = 2W + 2L\)

As all the answer choices are in terms of A, P and W, let us express L in terms of P and W

\(L = \frac{P}{2} - W\)

Substituting the above value of L in equation \(2A = 2*W*L\),

\(2A = 2*(W*L) = 2* W *( \frac{P}{2}-W)\)

Or, \(2A = WP - 2W^2\)

Or, \(2W^2 -WP+2A =0\)

Answer: E

Highlight portion is option B not E.
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p=2l+2w
a=lw
putting the values in option B we get as follows
2w^2-w(2l+2w)+2lw=2w^2-2lw-2w^2+2lw=0

Hence proved.
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Bunuel

Tough and Tricky questions: Geometry.



A rectangular circuit board is designed to have a width of W inches, a length of L inches, a perimeter of P inches, and an area of A square inches. Which of the following equations must be true?

A) 2W^2 + PW + 2A = 0
B) 2W^2 − PW + 2A = 0
C) 2W^2 − PW − 2A = 0
D) W^2 + PW + A = 0
E) W^2 − PW + 2A = 0

Kudos for a correct solution.

Source: Chili Hot GMAT

The correct answer is B.
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p = 2w + 2l ............ (1)

a = wl

Looking at the OA, we see that "l" is not present. Hence replacing \(l = \frac{a}{w}\) in equation (1)

\(p = 2w + 2\frac{a}{w}\)

\(pw = 2w^2 + 2a\)

\(2w^2 + 2a - pw = 0\)

Answer = B
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i just plugged it in real quick
l 2
w 4
a 8
p 12

Started with D, which immediatly made it clear that I need 2 times A within the same formula to get 0. This lead me to B.

Ans B
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