# What is the value of m?

6. $\left\{ 4,\;3,\;7,\;1\right\}$
If $m$ is a number so that the sum of $m$ and any number in the set above is also in the set, what is the value of $m$?

1. -1
2. -2
3. 4
4. 3
5. 0

m must be zero, because when we add zero to any number in the set will give us another number in the set.

\begin{align} \bigl\{4, 3, 7, 1\bigl\} +0=\begin{cases}
4+0=4\\
3+0=3\\
7+0=7\\
1+0=1
\end{cases}\end{align}