🔢 MathGrade 2Lesson 9
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Add 2- and 3-Digit Numbers

Lesson preview: the Mini Lesson and Vocabulary are open to everyone. Guided practice, exercises, the parent checklist and the printable PDF worksheet come with full access (free 7-day trial or membership).

Learning Objectives

  • 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
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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.
  • 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 10 always changes only the tens digit — the ones digit stays the same.

Adding hundreds: 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.
  • The same strategy works for any size number — the number line just stretches further!
Number line showing 14 plus 5 equals 19A number line from 10 to 20. A dot sits on 14. Five hops move forward one at a time to 19. A marker highlights 19 as the sum.14 + 5 = ?1011121314151617181920Start5 hops of +114 + 5 = 19
A number line from 10 to 20. Five orange hops move from 14 to 19, giving the sum 19.
Number line showing 120 plus 40 equals 160A number line from 100 to 180, marked in steps of 10. A dot on 120. Four hops of +10 each land at 130, 140, 150, 160.120 + 40 = ?100110120130140150160170180Start4 hops of +10120 + 40 = 160
A number line from 100 to 180. Four orange hops of +10 each move from 120 to 160, giving the sum 160.
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Ask yourself: "Where do I start? How many hops do I make? Where do I land?"

Vocabulary
Addend
A number that is added to anothere.g. In 14 + 5, both 14 and 5 are addends.
Sum
The answer when you add numberse.g. The sum of 14 + 5 is 19.
Number line
A line marked with numbers in ordere.g. I started at 14 on the number line.
Hop
A jump on a number line from one number to anothere.g. I made five hops forward to add 5.
Tens
Groups of tene.g. Adding 30 plus 20 means adding 5 tens.
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← Lesson 8: Solve Place Value RiddlesLesson 10: Subtract 2- and 3-Digit Numbers →