Super Subtraction: Taking Away 10s and 100s!

Math Grades 1st Grade 4:10 Video
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Lesson Description

Learn how to subtract 10 or 100 from bigger numbers using blocks and place value. We'll use our math skills to become subtraction superstars!

Video Resource

Subtracting ten or one hundred | Addition and subtraction within 100 | Early Math | Khan Academy

Khan Academy

Duration: 4:10
Watch on YouTube

Key Concepts

  • Place Value (Hundreds, Tens, Ones)
  • Subtracting 10
  • Subtracting 100

Learning Objectives

  • Students will be able to identify the place value of digits in a 3-digit number.
  • Students will be able to subtract 10 from a 3-digit number.
  • Students will be able to subtract 100 from a 3-digit number.

Educator Instructions

  • Introduction (5 mins)
    Start by reviewing place value with students. Ask them what the numbers in 324 mean (3 hundreds, 2 tens, 4 ones). Show them blocks or drawings to represent this number, similar to the video. Tell them that today, they will learn how to take away 10s and 100s from numbers!
  • Watching the Video (7 mins)
    Play the Khan Academy video 'Subtracting ten or one hundred'. Encourage students to pay attention to how the presenter uses blocks to subtract and how the digits change.
  • Subtracting 10 Practice (10 mins)
    Work through several examples of subtracting 10 from different 3-digit numbers (e.g., 456 - 10, 281 - 10, 639 - 10). Use blocks or drawings to model each problem. Emphasize that only the tens place changes when subtracting 10.
  • Subtracting 100 Practice (10 mins)
    Work through several examples of subtracting 100 from different 3-digit numbers (e.g., 527 - 100, 394 - 100, 815 - 100). Use blocks or drawings to model each problem. Emphasize that only the hundreds place changes when subtracting 100.
  • Mixed Practice (8 mins)
    Present students with problems that involve either subtracting 10 or 100 (e.g., 742 - 10, 295 - 100, 618 - 10). Have them identify whether they are subtracting 10 or 100 before solving. Encourage them to explain their reasoning.

Interactive Exercises

  • Place Value Bingo
    Create bingo cards with 3-digit numbers. Call out numbers like '10 less than 456' or '100 less than 821'. Students mark the corresponding number on their card. First to bingo wins!
  • Subtraction Station
    Set up a station with base-ten blocks and subtraction problems. Students use the blocks to model the subtraction and find the answers.

Discussion Questions

  • What happens to the number when we subtract 10?
  • What happens to the number when we subtract 100?
  • Which place value changes when you subtract 10? What about 100?

Skills Developed

  • Place Value Understanding
  • Subtraction Skills
  • Problem-Solving
  • Mental Math

Multiple Choice Questions

Question 1:

What number is in the tens place in 324?

Correct Answer: 2

Question 2:

What is 45 - 10?

Correct Answer: 35

Question 3:

What is 287 - 100?

Correct Answer: 187

Question 4:

Which place changes when you subtract 10?

Correct Answer: Tens

Question 5:

Which place changes when you subtract 100?

Correct Answer: Hundreds

Question 6:

What is 63 - 10?

Correct Answer: 53

Question 7:

What is 592 - 100?

Correct Answer: 492

Question 8:

What is 81 - 10?

Correct Answer: 71

Question 9:

What is 946 - 100?

Correct Answer: 846

Question 10:

If you have 238 blocks and take away 100, how many do you have left?

Correct Answer: 138

Fill in the Blank Questions

Question 1:

The number 324 has 3 ________.

Correct Answer: hundreds

Question 2:

If you take away 10 from 56, you get _______.

Correct Answer: 46

Question 3:

If you take away 100 from 295, you get _______.

Correct Answer: 195

Question 4:

When you subtract 10, the ________ place changes.

Correct Answer: tens

Question 5:

When you subtract 100, the ________ place changes.

Correct Answer: hundreds

Question 6:

67 - 10 = _______

Correct Answer: 57

Question 7:

412 - 100 = _______

Correct Answer: 312

Question 8:

The number 78 has 7 ________.

Correct Answer: tens

Question 9:

83 - 10 = _______

Correct Answer: 73

Question 10:

954 - 100 = _______

Correct Answer: 854

Educational Standards

1.NBT.C.5:Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used. 1.NBT.B.2:Understand that the two digits of a two-digit number represent amounts of tens and ones. Understand the following as special cases: 1.NBT.C.6:Subtract multiples of 10 in the range 10-90 from multiples of 10 in the range 10-90 (positive or zero differences), using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.

Teaching Materials

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