Castor.kim wrote:Dear GMAT volunteers,
This problem looks simple, but solve this problem incorrectly..
please someone tell me.. why 'A' is wrong..

[prob]
How many distinct integers are greater than x, but less than y?

(1) y=x+4
(2) x= √5

OA is C

I know that (2) is insufficient, and (1)+(2) is √5 < int < √5+4 ,so I can count the how many integers in that measures, sufficient
but,
in (1), problem said that x < a < y, and option (1) y=x+4 means..
x < a < x+4, so a have distinct 4 integers.. isn't it?? why wrong answer??

Let the STATEMENTS guide you.
Why does statement 2 indicates that x=√5 (approximately 2.2)?
Because this information likely has an effect upon STATEMENT 1.

Statement 1: y = x+4
If x=0, then y=0+4=4.
The number of distinct integers between 0 and 4 is THREE:
1, 2, 3.

If x=√5=2.2, then y=2.2+4 = 6.4.
The number of distinct integers between 2.2 and 6.2 is FOUR:
3, 4, 5 and 6.

Since the number of distinct integers between x and y can be different values, INSUFFICIENT.

Statement 2: x = √5
No information about y.
INSUFFICIENT.

Statements 1 and 2 combined:
As shown above, If x=√5=2.2, then y=2.2+4 = 6.4.
The number of distinct integers between 2.2 and 6.2 is FOUR.
SUFFICIENT.

The correct answer is C.

Great explanation!!
Thanks instructor!! I owe you one!!