Skill: Count backward by 1s, 10s, 100s, and 1,000s

To count backward, subtract the same amount each time:

• By $1$: subtract $1$.
• By $10$: subtract $10$.
• By $100$: subtract $100$.
• By $1{,}000$: subtract $1{,}000$.

The place value of the number tells you which digit usually changes.

Example: Count backward by $100$ from $6{,}203$.

Subtract $100$ each time:

$$\begin{aligned} 6{,}203-100&=6{,}103\\ 6{,}103-100&=6{,}003\\ 6{,}003-100&=5{,}903\\ 5{,}903-100&=5{,}803 \end{aligned}$$

So the count is:

$$6{,}203,\ 6{,}103,\ 6{,}003,\ 5{,}903,\ 5{,}803$$

Notice that the hundreds digit changes when possible. When counting from $6{,}003$ back $100$, the hundreds place is already $0$, so you regroup from the thousands place. That changes $6{,}003$ to $5{,}903$.

You can check each step by adding $100$ back to make sure you return to the previous number.