This GRE quantitative question requires you to understand how the units digit of integers change when they are squared.

If $n$ is a positive two digit integer, then which of the following CANNOT be the units digit of $n^2$?

1. $\quad 3$
2. $\quad 7$
3. $\quad 8$

1. $\quad \textrm{I only}$
2. $\quad \textrm{II only}$
3. $\quad \textrm{I and II only}$
4. $\quad \textrm{II and III only}$
5. $\quad \textrm{I, II, and III}$

 
This GRE Math practice problem tests your understanding of how to do unit conversions on algebraic quantities.

Water flows from a pipe at the rate of $3r$ gallons for every $m$ minutes. How much water flows through the pipe in $x$ seconds?

1. $\quad 3rxm$
2. $\quad \dfrac{3rx}{m}$
3. $\quad \dfrac{3rm}{x}$
4. $\quad \dfrac{20rx}{m}$
5. $\quad \dfrac{rx}{20m}$

 
This GRE Math practice problem tests your understanding of distributive property of multiplication.

$$ 998 \times 999 \times 1000 \times 1001 \times 1002$$
An increase of $1$ in which of the five numbers above would result in the greatest increase in the product?

1. $\quad 998$
2. $\quad 999$
3. $\quad 1000$
4. $\quad 1001$
5. $\quad 1002$

 
This GRE Math practice problem tests your understanding of percent change in the context of geometric area.

If the diameter of a circle is reduced by $40\%$, by what percent will the area of the circle be reduced?

1. $\quad 36$
2. $\quad 40$
3. $\quad 56$
4. $\quad 64$
5. $\quad 80$

 
This GRE quantitative comparison question tests your understanding of properties of isosceles triangles.

The lengths of two sides of an isosceles triangle are $3$ and $7$.

$\begin{array}{c c c c c c c c c c c}
& & & & & & \underline{\textrm{Quantity A}} & & & & \underline{\textrm{Quantity B}} \\
& & & & & & & & & & \\
& & & & & & \textrm{The perimeter of the triangle} & & & & \textrm{17} \\
\end{array}$

1. $\quad \textrm{Quantity A is greater.}$
2. $\quad \textrm{Quantity B is greater.}$
3. $\quad \textrm{The two quantities are equal.}$
4. $\quad \textrm{The relationship cannot be determined from the information given.}$