Add 2- and 3-Digit Numbers
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What you will learn
- 1Add 2- and 3-digit numbers by hopping forward on a number line
- 2Use the words addend and sum correctly
- 3Add by ones, tens, and hundreds to find the total
Mini Lesson
Adding means finding out how many there are altogether. One of the best ways to add is to use a number line — start at the first number and hop forward by the second number.
Key vocabulary
- The numbers you add together are called addends, and you can add them in any order (14 + 5 and 5 + 14 both make 19).
- The answer is called the sum.
- Each jump on the number line is called a hop.
Adding ones: 14 + 5
- Start at 14 on the number line.
- Hop forward 5 ones, one at a time: 15, 16, 17, 18, 19.
- You land on 19. So 14 + 5 = 19.
Adding tens: 30 + 20
- Start at 30. Hop forward in jumps of 10, twice: 40, 50.
- You land on 50. So 30 + 20 = 50.
- Adding a ten keeps the ones digit the same: 30, 40, 50.
Adding tens to a 3-digit number: 120 + 40
- Start at 120. Hop forward in jumps of 10, four times: 130, 140, 150, 160.
- You land on 160. So 120 + 40 = 160.
- Hundreds work the same way: for 200 + 300, start at 200 and hop 3 jumps of 100: 300, 400, 500.
Words to know
Addend
A number that is added to another
e.g. In 14 + 5, both 14 and 5 are addends.
Sum
The answer when you add numbers
e.g. The sum of 14 + 5 is 19.
Number line
A line marked with numbers in order
e.g. I started at 14 on the number line.
Hop
A jump on a number line from one number to another
e.g. I made five hops forward to add 5.
Tens
Groups of ten
e.g. 30 + 20 is 3 tens plus 2 tens, which makes 5 tens.
Ask yourself: "Where do I start? How many hops do I make (+ 0 means zero hops)? Where do I land?"
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