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If x = y + 2, where x, y are positive integers. Is (x + y) a multiple of 4 ?
(1) x is odd
(2) (3x + y) = 58
Given: x = y + 2 Target question: Is (x + y) a multiple of 4 ?This is a good candidate for
rephrasing the target question.
Since
x = y + 2, we can take the target question
Is (x + y) a multiple of 4 ? and replace x with y+2.
When we do this, we get:
Is (y+2 + y) a multiple of 4 ?Simplify:
Is (2y + 2) a multiple of 4 ?Factor to get:
Is 2(y + 1) a multiple of 4 ?We can see that, if y+1 is EVEN, then 2(y + 1) will be a multiple of 4
In order for y+1 to be EVEN,
we need y to be ODDSo, we can write:
REPHRASED target question: Is y odd?NOW ONTO THE STATEMENTS!!
Statement 1: x is odd We already know that
x = y + 2So, we can write:
ODD = y + 2This means:
ODD - 2 = ySince 2 is EVEN, we get:
ODD - EVEN = yThis means
y must be ODDSo, the answer to the REPHRASED target question is
YES, y IS oddSince we can answer the
REPHRASED target question with certainty, statement 1 is SUFFICIENT
Statement 2: (3x + y) = 58Since
x = y + 2, we can replace x with y+2 to get: 3(y + 2) + y = 58
At this point, we can see that we COULD solve this question to find the value of y, in which case, we COULD determine whether y is ODD.
Since we COULD answer the
REPHRASED target question with certainty, statement 2 is SUFFICIENT
Answer: D
RELATED VIDEO FROM OUR COURSE (rephrasing the target question)