K.1 Counting back to subtract - up to 10

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Counting Back to Subtract

Counting back is a way to subtract by starting at a number and saying the numbers in reverse order. Each number you say takes one away.

Examples:

Problem: 6 − 1 = ?
Solution: Start at 6. Count back one number: 5. So, 6 − 1 = 5.
Problem: 8 − 2 = ?
Solution: Start at 8. Count back two numbers: 7, 6. So, 8 − 2 = 6.

Helpful Hint

When you count back, always move to smaller numbers one step at a time.

Fingers can help us keep track of how many we subtract. Show the starting number in your head, then fold down one finger for each count back.

Examples:

Problem: 7 − 3 = ?
Solution: Start at 7 in your head. Fold down 1 finger (6), then another (5), then another (4). So, 7 − 3 = 4.
Problem: 5 − 2 = ?
Solution: Start at 5. Count back on two fingers: 4, 3. So, 5 − 2 = 3.

Helpful Hint

Say each number out loud as you fold a finger to avoid skipping a step.

A number line helps us see counting back. Start at the larger number and hop left one step for each number you subtract.

Examples:

Problem: 9 − 4 = ?
Solution: Start at 9. Hop back 4 steps: 8, 7, 6, 5. So, 9 − 4 = 5.
Problem: 10 − 2 = ?
Solution: Start at 10. Hop back 2 steps: 9, 8. So, 10 − 2 = 8.

Helpful Hint

Each hop on the number line shows one count back. Move left for every subtraction step.

We can use counting back to solve real-life subtraction stories. Start with the total, then count back to see how many remain.

Examples:

Problem: Mia has 6 apples. She eats 2. How many apples are left?
Solution: Start at 6. Count back 2: 5, 4. So, 6 − 2 = 4.
Problem: There are 9 frogs on a log. 3 jump off. How many frogs remain?
Solution: Start at 9. Count back 3: 8, 7, 6. So, 9 − 3 = 6.

Helpful Hint

Draw a number line or use your fingers to make the story problem easier to solve.

Counting back helps us solve problems in daily life, like sharing, eating, or losing items.

Real-Life Examples:

Problem: You have 5 pencils. You give 2 to a friend. How many are left?
Solution: Start at 5. Count back 2: 4, 3. So, 5 − 2 = 3.
Problem: There are 8 books on a shelf. 1 falls down. How many are still on the shelf?
Solution: Start at 8. Count back 1: 7. So, 8 − 1 = 7.

Try This

Make up your own subtraction stories. Use counting back with your fingers or a number line to solve them.