Negative numbers

Here's a number line that should look very familiar. It starts at $0$, then counts up by $1$ from there:

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We know that if we were to keep going to the right, we would have $11$, then $12$, and so on.

What happens if we keep going to the left of $0$ though? We get negative numbers! To the left of $0$ is $-1$, then $-2$, then $-3$, and so on:

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##Let's practice!

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##Why do we need negative numbers?

Negative numbers help us describe values less than zero.

###Example:

When the temperature is $8^\circ$ below $0^\circ$, it is less than $0$. We can say the temperature is $-8^\circ$.

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###A few more negative situations

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The opposite of a number is the number that is the same distance from $0$ on the number line, but on the other side of $0$.

Here are a couple of examples:

$\redD{-4}$ is the opposite of $\greenD4$.

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$\greenD3$ is the opposite of $\redD{-3}$.

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##Let's practice!

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##Challenge problems

**Use the following number line for the questions below.**

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