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Early Learners
Adding & Subtracting 2 and 3-Digit Numbers
Adding & Subtracting 2 and 3-Digit Numbers
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Adding and subtracting two and three digit numbers helps you count bigger groups in everyday life. You can use it to share pizza slices, count coins, read scores, or figure out time on a clock. Place value makes big numbers easier because each digit has a job. Hundreds, tens, and ones work together like colorful blocks in a math workshop.
When you add, you combine groups to find how many there are in all. When you subtract, you take away or compare to find what is left or how much more. Regrouping helps when ones or tens need to be traded, like 10 ones becoming 1 ten. Drawing blocks, coins, or simple pictures can make each step easier to see.
Key Facts
- A three digit number has hundreds, tens, and ones.
- 247 = 2 hundreds + 4 tens + 7 ones.
- Add ones first, then tens, then hundreds.
- Subtract ones first, then tens, then hundreds.
- 10 ones = 1 ten and 10 tens = 1 hundred.
- 58 + 36 = 94 and 94 - 36 = 58.
Vocabulary
- Digit
- A digit is one number symbol, such as 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9.
- Place value
- Place value tells what a digit is worth based on where it is in a number.
- Hundreds
- Hundreds are groups of 100, shown in the left place of a three digit number.
- Tens
- Tens are groups of 10, shown in the middle place of a three digit number.
- Regrouping
- Regrouping means trading ones, tens, or hundreds to help add or subtract.
Common Mistakes to Avoid
- Lining up numbers on the wrong side is wrong because ones must be under ones, tens under tens, and hundreds under hundreds.
- Starting with the hundreds place can cause errors because regrouping from the ones or tens may change the next place.
- Forgetting to carry a ten in addition is wrong because 10 ones must be traded for 1 ten.
- Subtracting the smaller digit from the larger digit in each column is wrong because subtraction must follow the order of the whole numbers.
Practice Questions
- 1 Add 46 + 37. Show how you regroup the ones.
- 2 Subtract 324 - 178. Show any regrouping in the tens or hundreds place.
- 3 Maya says 205 - 38 = 233 because she added instead of subtracted. Explain how you know the answer should be less than 205.