Skill: Subtract using the standard algorithm

Line up the numbers by place value, with ones under ones, tens under tens, and so on. Start subtracting at the ones place and move left.

Example:

$$\begin{array}{rrrrr} &5&0&0&0&0\\ -&2&7&8&4&6\\ \hline \end{array}$$

The ones column has $0-6$, so regroup. There are zeros in the tens, hundreds, and thousands places, so regroup across them:

• Take $1$ ten-thousand from the $5$ ten-thousands. This leaves $4$ ten-thousands.
• The $1$ ten-thousand becomes $10$ thousands. Give $1$ thousand to the hundreds, leaving $9$ thousands.
• The $1$ thousand becomes $10$ hundreds. Give $1$ hundred to the tens, leaving $9$ hundreds.
• The $1$ hundred becomes $10$ tens. Give $1$ ten to the ones, leaving $9$ tens.
• The ones become $10$ ones.

Now subtract each place from right to left:

$$\begin{array}{rrrrr} &4&9&9&9&10\\ -&2&7&8&4&6\\ \hline &2&2&1&5&4 \end{array}$$

So,

$$50{,}000-27{,}846=22{,}154.$$

Check by adding the difference to the number subtracted:

$$22{,}154+27{,}846=50{,}000.$$