Adding or Taking One Up to 10: One More and One Less

Every number up to 10 has a friend right before it and a friend right after it. The number right after is called "one more," and the number right before is called "one less." Finding one more than a number is the same as adding \( 1 \), and finding one less is the same as taking away \( 1 \).

For example, one more than \( 6 \) is \( 7 \), because \( 6 + 1 = 7 \). One less than \( 6 \) is \( 5 \), because \( 6 - 1 = 5 \). Learning this skill helps students move quickly between numbers without having to count everything from the beginning every time.

A number line is one of the easiest tools for this skill. To find one more than a number, hop one space to the right. To find one less, hop one space to the left. This connects nicely with the idea of number lines up to 10, where students learn to place and read numbers along a line.

Instead of drawing a number line every time, students can simply count on one number to find one more, or count back one number to find one less. This works hand in hand with counting up or down up to 10, since both skills rely on knowing what comes right before and right after a number.

It also helps to think about where a number sits among its neighbors, which is the same idea covered in before, between, or after a number up to 10. If a number comes right after another number, it is one more than it. If it comes right before, it is one less.

Example 1: What is one more than \( 3 \)? Count forward one step from \( 3 \): \( 3 + 1 = 4 \). So one more than \( 3 \) is \( 4 \).

Example 2: What is one less than \( 9 \)? Count backward one step from \( 9 \): \( 9 - 1 = 8 \). So one less than \( 9 \) is \( 8 \).

Example 3: A tray has \( 8 \) apples, and one more apple is added. How many apples are there now? Since one more means \( 8 + 1 \), there are now \( 9 \) apples.

Example 4: A basket has \( 10 \) balls, and one ball is taken out. How many balls are left? Since one less means \( 10 - 1 \), there are now \( 9 \) balls left.

Use small objects like blocks, buttons, or fingers to physically add one or take one away while saying the new total out loud. Practicing with numbers up to 10 in different orders builds confidence for later work with bigger numbers and full addition and subtraction problems.

Related lessons

• Kindergarten