Try the following GMAT Problem Solving question on how the average(arithmetic mean) of a data set changes when a data value is replaced by another number.

Question 54:

The average (arithmetic mean) of a list of $n$ numbers is $m$. If one of the numbers with a value of $6$ is replaced by another number of value $12$, then what is the new average for the list of $n$ numbers ?

1. $\quad \dfrac{m-6}{n}$

2. $\quad \dfrac{m+6}{n}$

3. $\quad \dfrac{m}{n}-6$

4. $\quad m-\dfrac{6}{n}$

5. $\quad m+\dfrac{6}{n}$

 
Try the following GMAT data sufficiency question on algebra involving equations and inequalities with two variables.

Question 53:

Is $ab=0$ ?

1. (1) $b < |b|$
2. (2) $ab = 2a$

1. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
2. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
3. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
4. EACH statement ALONE is sufficient.
5. Statements (1) and (2) TOGETHER are NOT sufficient.

 
Try the following GMAT Problem Solving question on finding prime factors of a summation.

Question 52:

If $S$ is the sum of the first fifty positive integers, then what is the sum of all the distinct prime factors of $S$ ?

1. $\quad 20$

2. $\quad 25$

3. $\quad 32$

4. $\quad 41$

5. $\quad 56$