Subtraction Within 20

Grade 1 · mathematics · 228 practice problems · read aloud

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Subtraction Within 20 ✏️

What is Subtraction?

Subtraction means taking away or finding the difference. We use it to find out how many are left, how many more one group has, or how much smaller something is. It's useful for sharing toys, counting cookies you've eaten, or seeing how many crayons are left in the box!

How to Subtract: Step-by-Step

  1. Start with the bigger number. This is the whole amount you begin with.
  2. Take away the smaller number. Count backwards, use your fingers, or imagine objects being removed.
  3. What's left is your answer! The number you have now is the difference.

Let's See Some Examples!

Example 1: 12 - 5 = ?

Imagine you have 12 strawberries. 🍓 You eat 5 of them. How many are left?

Start at 12. Count back 5: 11, 10, 9, 8, 7. You have 7 strawberries left! So, 12 - 5 = 7.

Example 2: 16 - 9 = ?

You can also think of a number line. Start at 16. Hop back 9 spots. You land on 7.

You can also use facts you know: 10 - 9 = 1. Then add the 6 back: 1 + 6 = 7.

Watch Out! Common Mistakes

Subtracting the wrong way: Remember, you always start with the bigger number! You can't do 5 - 12. If you have 5 cookies, you can't take away 12.

Counting mistakes: Be careful when counting backwards. Use your fingers or draw dots to help you keep track!

Tips & Tricks 🧠

  • Use your fingers! They are always with you.
  • Draw a picture. Cross out the ones you are taking away.
  • Think of addition. If 9 + 7 = 16, then 16 - 9 must be 7!
  • Learn the "Make a Ten" strategy: For 15 - 8, think "What do I add to 8 to make 15?" The answer is 7!

How to Practice

You can get better at subtraction by practicing a little every day!

  • Use flashcards.
  • Play online math games.
  • Ask a family member to give you quick problems like "What is 11 minus 4?"
  • Use small toys, blocks, or cereal pieces to act out subtraction stories.

Practice problems

6 of the 228, worked through step by step — try them before opening the answer.

1 0 - 0 = ?

Hint: Think about 0 - 0

Show the answer

Answer: 0

  1. Understand the problem We are subtracting 0 from 0. This means we start with 0 items and take away 0 items.
  2. Apply the subtraction operation When we subtract any number from itself, the result is always 0. For example: 5 - 5 = 0 10 - 10 = 0 Similarly, 0 - 0 = 0
  3. Verify with number line reasoning If we think of a number line starting at 0, and we subtract 0 (move 0 units to the left), we remain at position 0.
  4. Check with real-world example If you have 0 apples and you give away 0 apples, you still have 0 apples left.
  5. Final calculation 0 - 0 = 0 Therefore,

Step-by-step solution: the correct answer is 0.

2 1 - 0 = ?

Hint: Think about 1 - 0

Show the answer

Answer: 1

  1. We start with the problem: 1 - 0.
  2. Subtraction means taking away a certain quantity from another. Here, we are taking away 0 from 1.
  3. Taking away zero means we are removing nothing. The original amount, 1, remains unchanged.
  4. Therefore, 1 minus 0 equals 1. Final Answer: 1

3 1 - 1 = ?

Hint: Think about 1 - 1

Show the answer

Answer: 0

  1. Start with the given problem: 1 - 1.
  2. Understand the operation. The minus sign (-) means subtraction. We are taking away 1 from 1.
  3. Visualize the subtraction. If you have 1 object and you remove that 1 object, you are left with nothing.
  4. Perform the calculation. Subtracting a number from itself always results in zero. Therefore, 1 minus 1 equals 0.
  5. Write the final answer: 0.

4 2 - 0 = ?

Hint: Think about 2 - 0

Show the answer

Answer: 2

  1. Start with the given problem: 2 - 0.
  2. Understand the operation. Subtraction means taking away a certain quantity from another. Here, we are taking away 0 from 2.
  3. Visualize the process. If you have 2 objects and you remove 0 objects, you still have all 2 objects.
  4. Perform the calculation. Subtracting zero from any number does not change the number's value. Therefore, 2 minus 0 equals 2.
  5. Write the final answer. The result of 2 - 0 is 2.

5 2 - 1 = ?

Hint: Think about 2 - 1

Show the answer

Answer: 1

  1. Understand the operation. Subtraction means we start with the first number and remove the second number from it.
  2. Start with the first number. We start with 2.
  3. Remove the second number. We remove 1 from the 2 we started with.
  4. Count what remains. After removing 1 from 2, we have 1 left.
  5. Write the final answer. Therefore, 2 - 1 = 1.

Step-by-step solution: We are solving: 2 - 1 = ?

6 2 - 2 = ?

Hint: Think about 2 - 2

Show the answer

Answer: 0

  1. Understand the operation The minus sign (-) means we are subtracting. We are taking away 2 from the starting number 2.
  2. Visualize the process Imagine you have 2 objects. If you remove (subtract) 2 objects, you will have no objects left.
  3. Perform the calculation Start at the number 2 on the number line. Move 2 steps to the left (because we are subtracting). You will land at 0.
  4. Write the result 2 - 2 = 0 Final Answer: 0

Step-by-step solution: We start with the problem: 2 - 2

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