1.NBT.5: Finding 10 More or 10 Less
I can mentally find 10 more or 10 less than a two-digit number, without having to count.
What Your Child Needs to Know
This standard teaches your child to quickly find numbers that are 10 more or 10 less than any two-digit number using mental math strategies. For example, they learn that 10 more than 34 is 44, and 10 less than 67 is 57. This skill builds on their understanding of place value and helps them see patterns in our number system. It's an important foundation for mental math and prepares them for more complex addition and subtraction strategies.
Real World Practice
Visual models and hands-on activitiesVisual Models
Hundred Chart: Use a hundred chart to show that adding 10 means moving down one row, subtracting 10 means moving up one row.
Base-10 Blocks: Show 34 with 3 ten-rods and 4 unit cubes. Add one ten-rod to show 44 (10 more).
Number Line Jumps: Use a number line to show jumps of 10 forward or backward from any starting number.
Ten Frames: Use multiple ten frames to visually show adding or removing a complete group of 10.
Everyday Activities
Elevator Math: Pretend you're in a 10-story building. If you're on floor 23, what floor would you be on if you went up 10 floors? Down 10 floors?
Age Plus 10: Talk about how old family members would be in 10 years or were 10 years ago.
Calendar Counting: Look at dates on a calendar and find dates that are 10 days later or earlier.
Money Counting: Use dimes (worth 10 cents) to practice adding or subtracting 10 from amounts of money.
Quick Checks
Strategies and quick activitiesStrategies When Your Child Struggles
Focus on the Tens Place: Emphasize that only the tens digit changes when adding or subtracting 10.
Use the Hundred Chart: Show the pattern of moving up or down one row on a hundred chart.
Start with Multiples of 10: Begin with easier numbers like 20, 30, 40 before moving to mixed numbers.
Connect to Counting by 10s: Relate to their skip counting skills: 25, 35, 45, 55...
5-Minute Practice Activities
10 More/Less Race: Call out a number and have your child quickly say what's 10 more or 10 less.
Hundred Chart Hunt: Point to a number on a hundred chart and have your child find 10 more and 10 less.
Mental Math Challenge: Give 5 numbers and time how quickly your child can find 10 more for each.
Pattern Practice: Start with a number and count by 10s: "Start at 17: 17, 27, 37, 47..."
Check Progress
Track improvementDevelopmental Milestones
Beginning: Can find 10 more or 10 less using a hundred chart or by counting by 10s.
Developing: Finds 10 more or 10 less mentally for multiples of 10 (like 30, 40, 50).
Proficient: Quickly finds 10 more or 10 less for any two-digit number using mental strategies.
Advanced: Can explain the pattern and apply the strategy to solve word problems involving 10 more or 10 less.
What to Look For
Pattern Recognition: Your child notices that only the tens digit changes when adding or subtracting 10.
Mental Math: Can solve problems without counting by ones or using manipulatives.
Speed and Accuracy: Answers quickly and correctly for various two-digit numbers.
Strategy Explanation: Can explain why 34 + 10 = 44 using place value understanding.
Differentiation
Support for all learning levelsBelow Grade Level
Start with multiples of 10 and use visual supports like hundred charts. Practice with concrete manipulatives before moving to mental strategies.
Download Practice WorksheetAt Grade Level
Practice finding 10 more or 10 less for various two-digit numbers using mental math strategies. Focus on speed and accuracy.
Download Grade Level WorksheetAbove Grade Level
Extend to finding 10 more or 10 less across 100 (like 95 + 10 = 105) and solve multi-step word problems involving these concepts.
Download Challenge Worksheet