Mental Math 10 More/Less

Grade 1 · mathematics · 244 practice problems · read aloud

🔊 Listen to this explanation

Finding 10 More and 10 Less

🧠 What is it and Why is it Useful?

Finding "10 more" or "10 less" means quickly adding or taking away 10 from any number. This is a super skill because it helps you count faster and get ready for addition and subtraction! Think of it as moving up or down on a number chart.

🛤️ Step-by-Step Guide

  1. Look at the Tens Place: Find the digit in the tens place (the second number from the right).
  2. For 10 More: Add 1 to the digit in the tens place. The ones place stays the same! ➕1
  3. For 10 Less: Subtract 1 from the digit in the tens place. The ones place stays the same! ➖1

👀 Visual Examples

Example 1: What is 10 more than 34?

Step 1: The number is 34. The tens digit is 3.

Step 2: Add 1 to the tens digit: 3 + 1 = 4.

Step 3: Keep the ones digit the same: 4.

✅ Answer: 44

Example 2: What is 10 less than 67?

Step 1: The number is 67. The tens digit is 6.

Step 2: Subtract 1 from the tens digit: 6 - 1 = 5.

Step 3: Keep the ones digit the same: 7.

✅ Answer: 57

⚠️ Common Mistakes

Changing the Ones Digit: Remember, only the tens digit changes! If you start with 52, 10 more is 62, not 53.

Confusing More and Less: Take your time reading the question. Is it asking for 10 more or 10 less?

💡 Tips & Tricks

  • Use a 100s chart. To find 10 more, move down one row. To find 10 less, move up one row!
  • Think of it as a "fast elevator" that only stops on floors that end with the same number (ones digit).
  • Practice with "friendly" numbers like 20, 30, 40 to see the pattern easily.

🎯 How to Practice

  • Play "I Spy 10 More" with a 100s chart.
  • Use playing cards: draw a card, then say the number that is 10 more and 10 less.
  • Ask a partner to quiz you with numbers during car rides or commercial breaks!

Practice problems

6 of the 244, worked through step by step — try them before opening the answer.

1 0 + 10 = ?

Hint: Adding 10 increases the tens digit by 1.

Show the answer

Answer: 10

0 + 10 = 10. The tens digit increases from 0 to 1.

2 1 + 10 = ?

Hint: Adding 10 increases the tens digit by 1.

Show the answer

Answer: 11

1 + 10 = 11. The tens digit increases from 0 to 1.

3 2 + 10 = ?

Hint: Adding 10 increases the tens digit by 1.

Show the answer

Answer: 12

2 + 10 = 12. The tens digit increases from 0 to 1.

4 3 + 10 = ?

Hint: Adding 10 increases the tens digit by 1.

Show the answer

Answer: 13

3 + 10 = 13. The tens digit increases from 0 to 1.

5 4 + 10 = ?

Hint: Adding 10 increases the tens digit by 1.

Show the answer

Answer: 14

4 + 10 = 14. The tens digit increases from 0 to 1.

6 5 + 10 = ?

Hint: Adding 10 increases the tens digit by 1.

Show the answer

Answer: 15

5 + 10 = 15. The tens digit increases from 0 to 1.

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