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GMATPrep Problem - DS

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GMATPrep Problem - DS

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If 500 is the multiple of 100 that is closest to x and 400 is the multiple of 100 that is closest to y, which multiple of 100 is closest to x+y?

(1) x < 500
(2) y < 400

OA [spoiler]E[/spoiler]

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If 500 is the multiple of 100 that is closest to x and 400 is the multiple of 100 that is closest to y, which multiple of 100 is closest to x+y?

(1) x < 500
(2) y < 400

okay, so off the bat we can tell that 450
so 800
now this doesn't solve our answer, but it's a start. Let's correct our formulas for each part.
(1)
450 800
this tells us it's either 800 or 900, but not which one.

(2)
350 800 same as (1)

together
800
it could be either 800 or 900 still, so I'd go with E.

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An important take-away here is that if inequalities face the same way, they can be safely added. for example, if a>b and c>d, then it's safe to conclude that a+c>b+d.

However, one way in which inequalities are very different from equations is that you cannot subtract inequalities. If a>b and c>d, it is not safe to subtract one from the other and conclude that a-c>b-d. This may or may not be true.

The question above is GMATPrep question 1064. A detailed video solution of it is available.

-Patrick

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    Ask me about tutoring.

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