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G.4 Subtract two numbers up to three digits: word problems

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What is subtraction?

Subtraction is taking one number away from another to find the difference between them.

Example:
145
- 32
113

We start with 145 and take away 32, leaving us with 113.

Note

Think of subtraction as "how many are left" or "how much more one number is than another."

Subtracting without regrouping

When subtracting numbers where each digit in the top number is larger than the digit below it, we subtract directly without regrouping.

Example:
478
- 253
225

Start from the right: 8 - 3 = 5, 7 - 5 = 2, 4 - 2 = 2

Note

Always subtract from right to left, starting with the ones place.

Subtracting with regrouping

When a digit in the top number is smaller than the digit below it, we need to regroup (borrow) from the next place value.

Example:
523
- 187
336

Step-by-step: 3 - 7 (can't do), borrow from 2 tens → 13 - 7 = 6, 1 - 8 (can't do), borrow from 5 hundreds → 11 - 8 = 3, 4 - 1 = 3

Note

When you borrow, remember to reduce the number you borrowed from by 1.

Solving subtraction word problems

Word problems describe real-life situations where you need to subtract to find the answer. Look for key words that tell you to subtract.

Example Problem:

Sarah has 315 stickers. She gives 128 stickers to her friend. How many stickers does Sarah have left?

315
- 128
187

Sarah has 187 stickers left.

Note

Look for words like "left," "remain," "difference," "take away," or "how many more" to know when to subtract.

Different types of subtraction problems

Subtraction word problems can appear in many different real-world situations. Practice identifying what needs to be subtracted.

Examples:

Comparing amounts: The library has 427 books. 139 books are checked out. How many books are still in the library?

427
- 139
288


Finding how much more: Jake has 205 baseball cards. His brother has 168. How many more cards does Jake have?

205
- 168
37
Note

Read each problem carefully to understand what is being asked before you start subtracting.

Checking your subtraction

You can check your subtraction answer by adding it to the number you subtracted.

Example:

If 423 - 158 = 265, then 265 + 158 should equal 423.

265
- 158
423

Since 265 + 158 = 423, our subtraction was correct!

Note

Always check your work. Addition and subtraction are inverse operations - they undo each other.