1.NBT.6: Subtracting Multiples of 10

1. Base Ten Blocks

Use ten-rods to show problems. For 80 - 30, start with 8 ten-rods, take away 3 ten-rods, and count what's left (5 ten-rods = 50).

2. Bundled Objects

Use bundles of 10 straws or sticks. For 60 - 20, start with 6 bundles, remove 2 bundles, count remaining bundles.

3. Number Line Jumps

Draw a number line. For 70 - 40, start at 70 and make 4 backward jumps of 10 to land on 30.

4. Hundred Chart

Use a 1-100 chart. For subtracting 10, move up one row. For subtracting 20, move up two rows.

1. Money Problems

Use play money: "You have 80 cents and spend 30 cents. How much money do you have left?" Use dimes to represent tens.

2. Sticker Collections

Count stickers in groups of 10: "You had 90 stickers and gave away 40 stickers. How many do you have now?"

3. Toy Organization

Group toys by tens: "You had 70 blocks and put 20 blocks away. How many blocks are still out?"

4. Snack Time

Count snacks in groups: "We had 50 crackers and ate 20 crackers. How many crackers are left?"

5. Age and Time

Talk about decades: "Great-grandpa is 90 years old. 30 years ago, how old was he?"

1. Connect to Addition

If they know 30 + 40 = 70, then they can figure out 70 - 30 = 40. Use fact families to build understanding.

2. Use the "Think Tens" Strategy

For 80 - 50, say: "8 tens minus 5 tens equals 3 tens, which is 30."

3. Count Backwards by Tens

For 60 - 20, start at 60 and count back: "60, 50, 40." Practice counting backwards by tens regularly.

4. Make it Visual

Always use objects or drawings until the mental strategies become automatic.

5. Start with Smaller Numbers

If larger numbers are difficult, practice with 20 - 10, 30 - 10, 40 - 20 first.

Activity 1: Quick Tens Subtraction

Call out problems like "50 - 20" and have your child answer quickly. Build speed and confidence.

Activity 2: Number Line Hops

Draw a number line and practice "hopping" backwards by tens to solve subtraction problems.

Activity 3: Story Problems

Create simple stories: "There were 80 birds on a tree. 30 birds flew away. How many birds are left?"

Activity 4: Fact Family Practice

Practice related facts: "If 20 + 30 = 50, then 50 - 20 = ? and 50 - 30 = ?"

By the middle of the year, your child should:

• Subtract 10 from any multiple of 10 (50 - 10 = 40)
• Use objects or drawings to solve multiples of 10 subtraction
• Understand that only the tens place changes in these problems

By the end of the year, your child should:

• Subtract any multiple of 10 from any multiple of 10 mentally
• Recognize patterns in multiples of 10 subtraction
• Use multiple strategies (objects, number line, mental math) to solve problems
• Connect subtraction to addition using fact families

Simple Assessment:

Give your child problems like 70 - 40 and 90 - 30. Watch their strategy and ask them to explain.
Ask: "How would you solve 60 - 20?" Look for logical thinking and place value understanding.
Present a story problem: "You have 80 stickers and give away 50. How many do you have left?"