Bunuel wrote:
How old is Jane?
(1) Ten years ago she was one-third as old as she is now.
(2) In 15 years, she will be twice as old as she is now.
Target question: How old is Jane? Statement 1: Ten years ago she was one-third as old as she is now. Let x = Jane's PRESENT age
So, x - 10 = Jane's age TEN YEARS AGO
We can write: x - 10 = x/3
Multiply both sides by 3 to get: 3x - 30 = x
Subtract 3x from both sides: -30 = -2x
Solve: x = 15
The answer to the target question is
Jane is 15 years oldSince we can answer the
target question with certainty, statement 1 is SUFFICIENT
Statement 2: In 15 years, she will be twice as old as she is now Let x = Jane's PRESENT age
So, x + 15 = Jane's age FIFTEEN YEARS FROM NOW
We can write: 2x = x + 15
Subtract x from both sides: x = 15
The answer to the target question is
Jane is 15 years oldSince we can answer the
target question with certainty, statement 2 is SUFFICIENT
Answer: D
Cheers,
Brent
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