Exercises: Column Addition

1. Step: Add the ones.

$3+9=12$

This is more than 9. So you need to "drag the 10" one position to the left in order to "memorize" it.

$\begin{array}{cccc}& 9& 9& 9\\ +& & {}_{1}1& 3& \\ & & & 2\end{array}$

2. Step: Add the tens.

Don't forget to add the "remembered" tens.

$9+1+1=11$

This is more than 9. So drag the 10 one position forward to the 100s and thus "memorize" it.

$\begin{array}{cccc}& 9& 9& 9\\ +& {}_1& {}_{1}1& 3& \\ & & 1& 2\end{array}$

3. Step: Add the hundreds.

Don't forget to add the "remembered" hundredths.

$9+1=10$

Drag the 10 one step forward to the 1000s$\begin{array}{ccccc}& & 9& 9& 9\\ +& & {}_1& {}_{1}1& 3& \\ & 1& 0& 1& 2\end{array}$

The final result is $1012$.