Addition & Subtraction
Addition means putting groups together to find a total. Subtraction means taking away to find what is left. These two operations are the heart of early math.
Basic Addition
When you add, you combine two or more numbers to get a sum. The numbers being added are called addends.
Simple Facts
3 + 4 = 7 6 + 2 = 8 5 + 5 = 10
Using a Number Line
Start at 3 on the number line. Jump 4 spaces to the right. You land on 7.
A great strategy: always start with the larger number and count up. For 3 + 7, start at 7 and count up 3 more: 8, 9, 10.
Basic Subtraction
Subtraction finds the difference between two numbers. You start with a total and take away part of it.
Simple Facts
9 − 3 = 6 10 − 4 = 6 7 − 7 = 0
On a number line, subtraction means jumping left. Start at 9, jump 3 left: 8, 7, 6. Answer: 6.
Adding & Subtracting Two-Digit Numbers
Line up the ones column, then the tens column. Always start with the ones place.
Addition with Carrying
38 + 45 ---- 3 (carry the 1) 83
8 + 5 = 13. Write 3, carry 1. Then 3 + 4 + 1 = 8. Answer: 83.
Subtraction with Borrowing
52 - 27 ---- 25
You cannot do 2 − 7, so borrow 1 ten from the 5. Now 12 − 7 = 5, and 4 − 2 = 2. Answer: 25.
Word Problems
Read carefully and decide whether to add or subtract.
Add: "How many in all?"
Sam has 6 apples. He gets 8 more. How many does he have? 6 + 8 = 14
Subtract: "How many are left?"
There are 15 birds. 7 fly away. How many are left? 15 − 7 = 8
Key words for addition: altogether, total, in all, combined, more than. Key words for subtraction: left, remain, fewer, difference, take away.
Quick Quiz
Test what you just learned. Choose the best answer for each question.