# Is the sum of all the numbers between

Q) Is the sum of all the numbers between prime numbers x and y an even or an odd number?

1)    x = 3  y = 31
2)    y is the largest two digit number, x is even

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

To answer data sufficiency questions you don’t have to solve the problem. You just have to find the sufficient condition to prove the answer choice.

Question:  sum(x+1, x+2….y-1) = Odd or Even

Condition 1: x = 3  y = 31

Sum (4, 5,….30) = odd or Even

You don’t have to solve this but since you are aware of the sequence of numbers between x and y, the answer can be found.

Condition 1 is enough to answer the question

Condition 2: y is the largest two-digit number, x is even

The question mentions that x and y are prime numbers. Condition 2 provides two more additional information about the prime numbers.

Y is the largest two-digit number

Largest two-digit number is 99 but since question specifies that y is a prime number, y should be largest two digit prime number.

The only even prime number is 2. So x =2

Therefore we have to find the sum of all the numbers between  x = 2 and y= largest two digit prime number

Note: One mistake that test takers make is to spend time to find y, which is not necessary.
Once we get x and y, the sum can be calculated based on Arithmetic Progression. 1. Complete GMAT RC Questions in less than 1 minute and 50 seconds
3. Take Notes Effectively
4. Collect and Interpret Facts
5. Speed up Summary Creation
6. Remember Information
7. Question the Author

12. Learn to Answer GMAT organization of passage Question
13. Learn to identify the style/tone or attitude of the author

Mastering GMAT Critical Reasoning After you read F1GMAT’s Mastering GMAT Critical Reasoning Guide, you will learn:

How to overcome flawed thinking in GMAT Critical Reasoning?

How to spot Inconsistencies in Arguments

How to eliminate out of scope answer choices using Necessary and Sufficient Conditions

How to Paraphrase GMAT Critical Reasoning Question

How to Answer Assumption Question Type

How to Answer Conclusion Question Type

How to Answer Inference Question Type

How to Answer Strengthen Question Type

How to Answer Weaken Question Type

How to Answer bold-faced and Summary Question Types

How to Answer Parallel Reasoning Questions

How to Answer the Fill in the Blanks Question

Get F1GMAT's Newsletters (Best in the Industry)

• Ranking Analysis
• Post-MBA Salary Trends
• Post-MBA Job Function & Industry Analysis
• Post-MBA City Review
• MBA Application Essay Tips
• School Specific Essay Tips
• GMAT Preparation Tips