If x and y are positive, and 1/x percent of y equals 9y percent of x, what is the value of x?
(A) 1/81
(B) 1/3
(C) 3
(D) 9
(E) 81
Answer: B
Source: gmatprepnow.com
If x and y are positive, and 1/x percent of y equals 9y percent
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Important concept: k% = k/100Brent@GMATPrepNow wrote: ↑Fri Jun 24, 2022 6:17 amIf x and y are positive, and 1/x percent of y equals 9y percent of x, what is the value of x?
(A) 1/81
(B) 1/3
(C) 3
(D) 9
(E) 81
Answer: B
Source: gmatprepnow.com
So we can take our given information and write the following equation: [(1/x)/100](y) = (9y/100)(x)
Simplify: y/100x = 9xy/100
Multiply both sides of the equation by 100 to get: y/x = 9xy
Multiply both sides of the equation by x to get: y = 9x²y
Divide both sides by y to get: 1 = 9x²
Divide both sides by 9 to get: 1/9 = x², which means x = 1/3 or x = -1/3
Since we're told x is positive, we know that x = 1/3
Answer: B