length of x in inches

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by MartyMurray » Sat Mar 12, 2016 4:50 am
binaras wrote:The number of inches between two points is X. The number of inches in X is equal to the square root of the number of feet in X. (12 inches = 1 foot) What is the length of X in inches?

(A) 144
(B) 12
(C) 1
(D) 1/12
(E) 1/144
Translate exactly what is said into math.

X = the square root of the number of feet in X

Since 12 inches = 1 foot, X inches = X/12 feet.

X = √(X/12)

Square both sides.

X² = X/12

X² - (1/12)X = 0

Don't just divide X out. X is a factor! If you divide it out, you will lose a possible value of X.

X(X - 1/12) = 0

X = 0 or 1/12

0 is not given as an answer choice.

The correct answer is D.
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