# Basic Math

Subtraction is also a part of daily life. Let's say that you have $20.00 and you go to the store to buy a few things. You put a pizza in your cart that is $7.00. If you want to know how much money you have left to spend, you would subtract 7 from 20. You would find that you have $13 left to spend.

There are two important steps to subtracting whole numbers:

**1st**- Write the numbers vertically so that the place values are lined up in columns, like addition.**2nd**- Subtract only the digits with the same place value beginning with the ones place.

**In expanded notation:**

$$\begin{array}{r}\hfill \underset{\_}{\begin{array}{r}\hfill 300+70+5\\ \hfill -(200+10+2)\end{array}}\\ \hfill 100+60+3\end{array}$$

**Example:**

$$\begin{array}{r}\hfill \underset{\_}{\begin{array}{r}\hfill 375\\ \hfill -212\end{array}}\\ \hfill 163\end{array}$$

Some subtraction problems require borrowing. This would be necessary when the digit is smaller than the digit being subtracted. To borrow, you begin with the rightmost digit. Borrow from the digit to the left.

$\underset{\_}{\begin{array}{r}\hfill 937\to 900+30+7\\ \hfill -485\to 400+80+5\end{array}}$

Starting at the right, you can take away 5 from 7. Look at the tens place. You cannot subtract 8 from 3 (or 80 from 30) so you must borrow 100 from 900.

We are going to "borrow" 100 from 900 and give it to the 10s place.

$\begin{array}{c}\underset{\_}{\begin{array}{l}\text{\hspace{0.05em}}\text{\hspace{0.05em}}\text{\hspace{0.05em}}\text{\hspace{0.05em}}\text{\hspace{0.05em}}\text{\hspace{0.05em}}\text{\hspace{0.05em}}\text{\hspace{0.05em}}937{\to}^{8}\text{\hspace{0.17em}}\overline{)9}00{+}^{1}30+7\hfill \\ -485\to \text{\hspace{0.05em}}\text{}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}400+\text{\hspace{0.05em}}\text{\hspace{0.05em}}\text{\hspace{0.05em}}\text{\hspace{0.05em}}\text{\hspace{0.05em}}\text{\hspace{0.05em}}80+5\hfill \end{array}}\\ \text{\hspace{0.05em}}\text{}\text{}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}452\to \text{\hspace{0.17em}}\text{\hspace{0.17em}}400+\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}50+2\end{array}$

Now you can subtract 80 from 130. The answer is 50 which means 5 tens. Finally, subtract 400 from 800. Remember, you borrowed 100 from 900! 800 - 400 = 400, or 4 in the hundreds place. The final answer is 452.

Let's see how you do with a few practice problems!

**Instructions:** Subtract the following:

$\underset{\_}{\begin{array}{r}\hfill 343\\ \hfill -47\end{array}}$