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Round, Add, and Subtract Two- and Three-Digit Numbers

Unit Plan

Round, Add, and Subtract Two- and Three-Digit Numbers

Objectives

In this unit, students will round, add, and subtract two- and three-digit numbers. More specifically, they will:

  • round two-digit and three-digit numbers to the nearest ten.
  • round three-digit numbers to the nearest hundred.
  • add two-digit and three-digit numbers using the standard algorithm.
  • subtract two-digit and three-digit numbers using the standard algorithm.

Essential Questions

  • How is mathematics used to quantify, compare, represent, and model numbers?
  • How are relationships represented mathematically?
  • What does it mean to estimate or analyze numerical quantities?
  • What makes a tool and/or strategy appropriate for a given task?
  • When is it appropriate to estimate versus calculate?

Related Unit and Lesson Plans

Related Materials & Resources

The possible inclusion of commercial websites below is not an implied endorsement of their products, which are not free, and are not required for this lesson plan.

Rounding

 

Addition and Subtraction

Formative Assessment

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    Multiple-Choice Items:

    1. Ellana bought a new backpack that cost $32. About how much did the backpack cost, rounded to the nearest ten dollars?

    A

    $30

    B

    $32

    C

    $35

    D

    $40

     

    1. Takumi and his family drove 461 miles to see his grandparents. About how many miles did Takumi and his family drive, rounded to the nearest hundred?

    A

    400

    B

    460

    C

    470

    D

    500

     

    1. Lucia and her parents paid $450 for a new laptop computer. About how much did the computer cost, rounded to the nearest hundred dollars?

    A

    $400

    B

    $450

    C

    $500

    D

    $550

     

    1. Nico read 25 pages in a book. The next day he read 38 more pages. How many pages did Nico read in all?

    A

    53

    B

    63

    C

    64

    D

    74

     

    1. At Tiago’s school, there are 153 boys and 142 girls in third grade. How many third grade students are there in all?

    A

    293

    B

    295

    C

    305

    D

    383

     

    1. Both Olivia and Laura went to summer camp. Olivia’s camp cost $435. Laura’s camp cost $575. How much did it cost in all for Olivia and Laura to go to summer camp?

    A

    900

    B

    910

    C

    1010

    D

    1100

     

    1. Hugo and Zachary played a video game. Hugo had 661 points and Zachary had 536 points. How many more points did Hugo have than Zachary?

    A

    $125

    B

    $128

    C

    $135

    D

    $136

     

    1. Ms. Lewis had 96 pencils. She gave 23 pencils to her students. How many pencils does she have left?

    A

    73

    B

    79

    C

    83

    D

    89

     

     

     

    1. Pablo had $85 to spend on snacks for the school picnic. He spent $36. How much money does Pablo have left?

    A

    $31

    B

    $39

    C

    $41

    D

    $49

     

    Multiple-Choice Answer Key:

    1. A

    2. D

    3. C

    4. B

    5. B

    6. C

    7. A

    8. A

    9. D

     

     

    Short-Answer Items:

    1. There are 537 gumballs in a gumball machine. Round 537 to the nearest hundred and explain your thinking.

     

     

    1. The zoo is home to two of the largest living birds, ostriches. One weighs 234 pounds and the other weighs 258 pounds. What is the total weight of these two ostriches? Write an equation to show your answer.

     

     

    1. Last summer Ryan earned $68 mowing lawns. This summer he earned $93. How much more did he earn this summer than last? Write an equation to show your answer.

     

     

    Short-Answer Key and Scoring Rubrics:

    1. There are 537 gumballs in a gumball machine. Round 537 to the nearest hundred and explain your thinking.

    The result is 500 when 537 is rounded to the nearest hundred. A correct explanation may include that 537 is between 500 and 600, and less than the halfway point of 550. For this reason, 537 is closer to 500 and is rounded to 500.

     

    Points

    Description

    2

    The student rounds the number correctly and provides a correct explanation.

    1

    The student rounds the number correctly or provides a correct explanation.

    0

    The student does not round the number correctly or provide a correct explanation.

     

    1. The zoo is home to two of the largest living birds, ostriches. One weighs 234 pounds and the other weighs 258 pounds. What is the total weight of these two ostriches? Write an equation to show your answer.

    A correct equation expresses this as an addition problem, 234 +258. The correct sum is 492, or 234 + 258 = 492.

    Points

    Description

    2

    The student provides an accurate equation and the correct sum.

    1

    The student provides an accurate equation or the correct sum.

    0

    The student does not provide the accurate equation or the correct sum.

     

     

    1.  Last summer Ryan earned $68 mowing lawns. This summer he earned $93. How much more did he earn this summer than last? Write an equation to show your answer.

    A correct equation expresses this as subtraction problem, 93 – 68. The correct difference is 25, or 93 – 68 = 25.

     

    Points

    Description

    2

    The student provides an accurate equation and the correct difference.

    1

    The student provides an accurate equation or the correct difference.

    0

    The student does not provide an accurate equation or the correct difference.

     

     

     

    Performance Assessment:

    Jacob’s family went on vacation for one week. Jacob’s family spent $75 in Yellowstone National Park. They spent $48 at Mount Rushmore.

     

    1. Rounded to the nearest ten dollars, about how much money did Jacob’s family spend at Yellowstone National Park?

     

     

    1. What was the total amount of money Jacob’s family spent at Yellowstone National Park and Mount Rushmore?

     

    1. How much more did Jacob’s family spend at Yellowstone National Park than at Mount Rushmore?

     

    While on vacation, Jacob’s family spent $586 staying at hotels. They spent $218 for food.

     

    1. Rounded to the nearest hundred dollars, about how much did Jacob’s family spend on food?

     

    1. What was the total amount of money Jacob’s family spent on hotels and food for their vacation?

     

     

    1. How much more money did Jacob’s family spend on hotels than on food during their vacation?

     

    Jacob spent $11 on a deck of cards with “South Dakota” printed on the back. He also spent $17 on a book about South Dakota history.

     

    1. Rounded to the nearest ten, about how much did Jacob spend on both items together?

     

     

    1. Rounded to the nearest ten, about how much did Jacob spend on the book?

    Answers:

    1. 80
    2. 123
    3. 27
    4. 200
    5. 804
    6. 368
    7. 30
    8. 20

     

     

     

    Performance Assessment Scoring Rubric:

    Points

    Description

    4

    • All answers are complete and correct.
    • Work is shown and demonstrates clear understanding of place value as pertaining to rounding, adding, and subtracting multidigit numbers.
    • The student demonstrates advanced understanding of rounding to the nearest ten or hundred and adding or subtracting two-digit and three-digit numbers.

    3

    • Most answers are complete and correct.
    • Work is shown for most problems and all requirements of the problems are met.
    • The student demonstrates a strong understanding of rounding to the nearest ten or hundred and adding or subtracting two-digit and three-digit numbers.

    2

    • Many answers are complete and correct.
    • Little work is shown and it fails to meet all the requirements of the problems.
    • The student demonstrates a limited understanding of rounding to the nearest ten or hundred and adding or subtracting two-digit and three-digit numbers.

    1

    • Some answers are complete and correct.
    • Very little correct work is shown.
    • The student demonstrates a very limited understanding of rounding to the nearest ten or hundred and adding or subtracting two-digit and three-digit numbers.

    0

    • Very few or no answers are correct.
    • No work attempted or no work shown is correct.
    • The student demonstrates no understanding of rounding to the nearest ten or hundred and adding or subtracting two-digit and three-digit numbers
Final 04/12/13
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