Subtract a 1-digit number from a 3-digit number

Subtracting One-Digit Numbers from Three-Digit Numbers

• When subtracting a 1-digit number from a 3-digit number, the same rules that apply to subtracting from 1 or 2-digit numbers are used.
• Tools like number lines, place value charts, partitioning, and Base 10 are valuable aids when subtracting.

Examples

Example 1: What is 321 - 4?
Sol: This is 321 using Base 10.

There's only 1 one. How are you supposed to subtract 4 ones from 321?
Remember, one ten is the same as ten ones, so you could turn one of the ten sticks into ten ones. Then you have plenty of ones to subtract from!
Now you can take away 4 of the cubes.
You have the answer: 421 - 4 = 317

Example 2: What is 632 - 5?
Sol: A number line can help you answer this question.
Find 632 on the number line and then count 5 steps backwards:
Now you have the answer:
632 - 5 = 627
Since you had to go through a ten for that questions, you could have also used your number bond and partitioning skills to reach the ten before subtracting the rest of the number.
Partitioning the 5 into 2 and 3 is a way to subtract quickly, particularly if you are doing the calculation in your head.
First, partition the 5:

Now apply this to the number line.

A different method, but the same answer - 627.