If [x] Denotes The Least Integer Greater Than or Equal to x GMAT Problem Solving

Question: If [x] denotes the least integer greater than or equal to x and [x/2] = 0, which of the following could be the value of x?

  1. -2
  2. -3/2
  3. 1/2
  4. 1
  5. 2

Correct Answer: B

Solution and Explanation
Approach Solution 1:

Given: x denotes the least integer greater than or equal to x and [x/2] = 0
Find out: The value of x

First, let's take a moment to get a good idea of what this strange notation means.
A few examples:

[5.1] = 6
[3] = 3
[8.9] = 9
[-1.4] = -1
[-13.6] = -13

So, if [x/2] = 0, then 
As per the basic arithmetic function, we know that -1 < x/2 ≤ 0
If we Multiply all sides of the inequality by 2 we get: 
-2 < x ≤ 0

As per the answer choices given in the question, 
Only -3/2 falls inside that range (-2 < x ≤ 0)

Hence, the correct answer is B.

Approach Solution 2:
Given: x denotes the least integer greater than or equal to x and [x/2] = 0
Find out: The value of x

Since [x] denotes the least integer greater than or equal to x
This means x = I , if x is an integer and x = I
x = i+1, if x is not an integer and x = i + d where i is integral part of x and d is decimal part of x

So [x/2] = 0
-1 < x/2 < = 0
-2 < x <= 0

Only -3/2 which is equal to -1.5 lies in between this range.

Hence, the correct answer is option B.

Approach Solution 3:
If [x/2]=0 then x/2 is a number such that the least integer greater than or equal to x/2 is 0. We can rewrite this as the inequality x/2≤0. Then, the value of x in C, D and E is wrong because they are positive numbers, then x/2 would be a positive number which contradicts this inequality.

Now, 0 is the least integer that satisfies this inequality, therefore we cannot have that x/2≤-1 since -1 is an integer and -1<0. Then x/2>-1. This discards A as wrong, because for x=-2, x/2=-1, contrary to x/2>-1.

Thus B is the right answer. To verify, if x=-3/2, then x/2=-3/4 and we have that -1<-3/4≤0 as required.

“If [x] denotes the least integer greater than or equal to x”- is a topic of the GMAT Quantitative reasoning section of GMAT. This question has been taken from the book "The Official Guide for GMAT Review 2017". To solve GMAT Problem Solving questions a student must have knowledge about a good amount of qualitative skills. GMAT Quant practice papers improve the mathematical knowledge of the candidates as it represents multiple sorts of quantitative problems.


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