Complete the Subtraction Statement Up to 10

A subtraction statement has three parts: the number you start with, the number you take away, and the number left over. For example, \( 8 - 5 = 3 \) means we started with 8, took away 5, and 3 is left. When one of these three numbers is hidden, our job is to figure out what it must be so the statement stays true. We show the missing number with a blank box, like \( 8 - \Box = 3 \).

This skill builds on simpler subtraction ideas, such as taking away with objects up to 10. Once counting and taking away feel comfortable, filling in a missing number is really just the same idea worked backward.

The easiest way to complete a subtraction statement is to picture (or draw) the starting group, cross some out, and count what is left. Suppose the statement is \( 7 - \Box = 4 \). Draw 7 objects, then cross out objects one at a time until only 4 remain. Count how many you crossed out, and that count is the missing number.

A ten-frame makes it easy to see the whole group at once. Fill the frame with the starting number of counters, then imagine removing some until you reach the amount left. The number of counters you removed is the missing number in the statement.

Here the ten-frame starts with 8 filled counters. Three of them (shown as empty circles) are removed, leaving 5. That completes the statement \( 8 - 3 = 5 \).

A number line is another handy tool once objects and ten-frames feel familiar. Start at the first number in the statement and hop backward one space for each number taken away, or count the hops it takes to land on the answer. This method is covered in more detail in subtracting with a number line up to 10, and it works well for statements with a missing subtrahend, like \( 9 - \Box = 6 \), since you can count the hops from 9 down to 6.

Example 1: Complete \( 6 - \Box = 2 \).

Start with 6 objects. Take away objects until only 2 are left. Since \( 6 - 4 = 2 \), the missing number is 4.

Example 2: Complete \( \Box - 4 = 5 \).

Here the starting number is missing. Think: what number, once 4 is taken away, leaves 5? Add 4 and 5 together to check: \( 5 + 4 = 9 \), so the missing number is 9, and \( 9 - 4 = 5 \).

Example 3: Complete \( 10 - 6 = \Box \).

Here the difference is missing, which is the most familiar type of subtraction. Counting back 6 from 10 lands on 4, so \( 10 - 6 = 4 \).

A quick way to check any completed statement is to add the part that was taken away back to the part that is left. If the total matches the number you started with, the missing number is correct. This connects nicely to practice with subtraction word problems up to 10, where checking an answer this way helps confirm a story problem was solved correctly.

Related lessons

• Kindergarten