Is x+y equal to 3.6 ? I need help here

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Is x+y equal to 3.6 ? I need help here

by Vincen » Mon Sep 25, 2017 6:22 pm
Is x+y equal to 3.6 ?

(1) x > 1.7 or x = 1.7
(2) y > 1.9

The OA is C.

I know each statement alone is not sufficient, but why together they are sufficient? If y=2 and x=1.7 then x+y=3.7. What is wrong with my calculus?

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The key here is to recognize that this is a "yes"/"no" Data Sufficiency question. This means that the statement is sufficient if we can prove EITHER 1) that, yes, x + y will always equal 3.6 OR 2) that, no, x + y will never equal 3.6.

When we combine the statements, we know that x is, at its smallest, 1.7.
If x = 1.7 and x+y=3.6:

1.7 + y = 3.6
y = 1.9

However, we know that y must be greater than 1.9. So we know for a fact that x + y will never equal 3.6: x + y will always be greater than 3.6. This is sufficient to answer "no", so the statements are sufficient together.
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