melguy wrote:Please help me with this question.
If I plug in 2 for both x and y then A and E yield the same result. I cannot think of any other number that fits the criteria (x+y = xy). Is there a way to solve it with plugging in numbers?
Thanks
Strategy:
PLUG IN for x and solve for y.
Case 1: x=2
If we plug x=2 into (x+y)/(xy), we get:
(2+y)/(2y) = 1
2+y = 2y
y =
2.
Since the question stem asks for the value of y, the value in blue is our target.
Now we plug x=2 into the answer choices to see which yields our target of 2.
In this case, two answer choices work:
A: x/(x-1) = 2/(2-1) = 2.
E: x = 2.
To determine whether the correct answer is A or E, TEST A SECOND CASE.
Case 2: x=3
If we plug x=3 into (x+y)/(xy), we get:
(3+y)/(3y) = 1
3+y = 3y
3 = 2y
y =
3/2.
Since the question stem asks for the value of y, the value in blue is our target.
Now we plug x=3 into A and E to see which yields our target of 3/2.
A: x/(x-1) = 3/(3-1) = 3/2.
E: x = 3.
Only
A works.
The correct answer is
A.
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