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Mathematics

Mathematics. Chapter 1: Addition & Subtraction with regrouping Grassy Lake Elementary School Third Grade Created by: Mrs. Tamara Russell. Goals. To identify and write related addition and subtraction facts. To solve number sentences for missing addends.

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Mathematics

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  1. Mathematics Chapter 1: Addition & Subtraction with regrouping Grassy Lake Elementary School Third Grade Created by: Mrs. Tamara Russell

  2. Goals • To identify and write related addition and subtraction facts. • To solve number sentences for missing addends. • To add 2-digit numbers without regrouping. • To subtract 2-digit numbers without regrouping. • To use the problem solving skill choose the operation.

  3. Materials • Scrap paper or white boards • Pencils or expo markers • Erasers or paper towels for the boards

  4. 56 62 +15 - 15 71 47 Today’s Lesson • By the end of today’s lesson, you will be able to add and subtract two digit numbers using regrouping. 1 5 1

  5. Lesson • Did you know that every number has a home, just like you? • We call those numbers homes their place value. • In order to add or subtract two digit numbers we need to review place value! • Let’s go!

  6. Let’s do some problems! • You will need a white board, a marker and an eraser. • Together we will do six problems – three addition and three subtraction. • When we are all done, we should know how to add and subtract by regrouping!  • Let’s do it!

  7. Tens Ones Two digit addition 1 • Always remember to line up your numbers properly. • Start at the right. (6 + 5) • Put the sum of 6 + 5 in its house. (11) Oops! Too many! Carry a number! • Now, add the numbers in the tens’ column. (5 + 1 + 1) • Put the sum of 5 + 1 + 1 in the tens’ column. (7) 5 6 + 1 5 7 1

  8. Tens Ones Again? 1 • Always remember to line up your numbers properly. • Start at the right. (4 + 6) • Put the sum of 4 + 6 in its house. (10) Oops! Too many! Carry a number! • Now, add the numbers in the tens’ column. (2 + 3 + 1) • Put the sum of 2 + 3 + 1 in the tens’ column. (6) 2 4 + 3 6 6 0

  9. Tens Ones Last time? 1 • Always remember to line up your numbers properly. • Start at the right. (2 + 9) • Put the sum of 2 + 9 in its house. (11) Oops! Too many! Carry a number! • Now, add the numbers in the tens’ column. (3 + 1 + 1) • Put the sum of 3 + 1 + 1 in the tens’ column. (5) 3 2 + 1 9 5 1

  10. Tens Ones Let’s subtract! • Always remember to line up your numbers properly. • Start at the right. (3 - 4) Oops! You can’t subtract 4 from 3! Time to borrow! • Borrow ten from next door and make 13. And subtract a ten to make 6. • Now, subtract. (13 – 4) Put your answer in the ones place. • Last, subtract 6 – 3. Put your answer in the tens place! 7 3 6 13 - 3 4 3 9

  11. Tens Ones Again? • Always remember to line up your numbers properly. • Start at the right. (2 - 4) Oops! You can’t subtract 4 from 2! Time to borrow! • Borrow ten from next door and make 12. And subtract a ten to make 6. • Now, subtract. (12 – 4) Put your answer in the ones place. • Last, subtract 3 – 2. Put your answer in the tens place! 4 2 3 12 - 2 4 1 8

  12. Tens Ones Last time! • Always remember to line up your numbers properly. • Start at the right. (5 - 9) Oops! You can’t subtract 5 from 9! Time to borrow! • Borrow ten from next door and make 15. And subtract a ten to make 7. • Now, subtract. (15 – 9) Put your answer in the ones place. • Last, subtract 7 – 7. The answer is zero and does not change the amount in the number, so you don’t have to put it there! 8 5 7 15 - 7 9 6

  13. 1 5 14 4 0 6 1 6 18 7 1 1 9 Independent work • Complete these practice problems on your white board. Raise your hand when you are done so that I can check your work! • You have ten minutes to work and then I’ll show you the answers.

  14. Fantastic! How did I get such smart cookies? Tomorrow’s Lesson: Working on addition and subtraction story problems

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