Add Multiples of 10

Grade 1 · mathematics · 65 practice problems · read aloud

🔊 Listen to this explanation

Adding Multiples of 10

🧠 What is it and Why is it Useful?

Adding multiples of 10 means adding numbers like 10, 20, 30, 40, and so on. It's a super useful skill because it helps you count big numbers quickly, like counting how many crayons are in several boxes!

📝 How to Solve Problems: Step-by-Step

  1. Look at the tens. Find the digits in the tens place (the first digit).
  2. Add the tens. Just add those first digits together like normal numbers.
  3. Bring the zero! Don't forget to put a 0 at the end of your answer.

👀 Let's Look at Examples

Example 1: 30 + 40 = ?

  • Step 1: Look at the tens. We have 3 and 4.
  • Step 2: Add the tens. 3 + 4 = 7.
  • Step 3: Bring the zero! 7 becomes 70.
  • Answer: 30 + 40 = 70 🎉

Example 2: 20 + 50 = ?

  • Step 1: Look at the tens. We have 2 and 5.
  • Step 2: Add the tens. 2 + 5 = 7.
  • Step 3: Bring the zero! 7 becomes 70.
  • Answer: 20 + 50 = 70 🎉

🚨 Common Mistakes to Avoid

Forgetting the Zero! The biggest mistake is adding the tens but forgetting to put the 0 at the end. Remember, 2 + 5 is 7, but 20 + 50 is 70, not 7!

Adding the Ones Place: With multiples of ten, the ones place is always 0. You don't need to add it! Just focus on the tens.

💡 Tips & Tricks

Think of Dimes! One dime is 10 cents. If you have 2 dimes (20 cents) and 5 dimes (50 cents), how many dimes do you have? 7 dimes, which is 70 cents!

The "Zero Hero" Rule: The zero at the end is the hero of the problem. It's always there to help you make a bigger number!

🎯 How to Practice

  • Use base-ten blocks. A "rod" is 10. Practice combining rods to find the total.
  • Play a game: Write multiples of 10 on index cards. Flip over two cards and race to say the sum!
  • Try these problems: 10 + 30, 40 + 20, 50 + 10, 60 + 30.

Practice problems

6 of the 65, worked through step by step — try them before opening the answer.

1 20 + 30 = ?

Hint: Think about adding groups of ten. For example, 10 + 40 means one ten plus four tens.

Show the answer

Answer: 50

  1. Identify the numbers to be added. We have the number 20 and the number 30.
  2. Understand what addition means. Addition is the process of combining two or more numbers into a single total sum.
  3. Break down the numbers by place value. The number 20 is 2 tens and 0 ones. The number 30 is 3 tens and 0 ones.
  4. Add the digits in each place value column, starting with the ones place. Ones place: 0 + 0 = 0 Tens place: 2 + 3 = 5
  5. Combine the results from each column. We have 5 tens and 0 ones. This makes the number 50.
  6. State the final answer. Therefore, 20 + 30 = 50.

2 30 + 40 = ?

Hint: Think about adding the tens first, then combine them. For example, when adding 20 and 50, you add 2 tens and 5 tens to get 7 tens.

Show the answer

Answer: 70

  1. Identify the numbers to be added. We have 30 and 40.
  2. Add the numbers in the ones place first. The number 30 has a 0 in the ones place. The number 40 also has a 0 in the ones place. 0 + 0 = 0 So, the ones digit of our answer is 0.
  3. Add the numbers in the tens place. The number 30 has a 3 in the tens place, which represents 3 tens, or 30. The number 40 has a 4 in the tens place, which represents 4 tens, or 40. 3 tens + 4 tens = 7 tens, or 70.
  4. Combine the results from the tens and ones places. From Step 3, we have 7 tens (70). From Step 2, we have 0 ones (0). 70 + 0 = 70.
  5. State the final answer. Therefore, 30 + 40 = 70.

3 50 + 30 = ?

Hint: Think about adding the tens first, then combine them.

Show the answer

Answer: 80

  1. Look at the tens place in both numbers. 50 has 5 tens, and 30 has 3 tens.
  2. Add the tens together: 5 tens + 3 tens = 8 tens.
  3. 8 tens equals 80.

The answer is 80.

4 40 + 50 = ?

Hint: Think about adding the tens first, then combine them.

Show the answer

Answer: 90

  1. Look at the tens place in both numbers. 40 has 4 tens, and 50 has 5 tens.
  2. Add the tens together: 4 tens + 5 tens = 9 tens.
  3. 9 tens equals 90.

The answer is 90.

5 50 + 40 = ?

Hint: Think about adding the tens first, then combine them.

Show the answer

Answer: 90

  1. Look at the tens place in each number. 50 has 5 tens, and 40 has 4 tens.
  2. Add the tens together: 5 tens + 4 tens = 9 tens.
  3. 9 tens is the same as 90.

The answer is 90.

6 60 + 40 = ?

Hint: Think about adding the tens places together

Show the answer

Answer: 100

  1. Start with 60
  2. Add 40 to get 60 + 40
  3. 60 + 40 = 100

The answer is 100.

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