# Lesson Video: Subtracting by Counting Back: Numbers up to 10 Mathematics • 1st Grade

In this video, we will learn how to subtract within 10 by counting back from the starting number.

08:49

### Video Transcript

Subtracting by Counting Back: Numbers up to 10

In this video, we will learn how to subtract within 10 by counting back from the starting number. We can use a number line to help us count back or subtract.

Let’s practice counting back from 10. 10, nine, eight, seven, six, five, four, three, two, one, zero. Let’s think about how we can use counting back on a number line or a number track to help us subtract. How could we calculate 10 subtract four using a number line? If the amount we start with is 10, then we need to start at number 10 on the number line. We need to subtract four from 10. So, we need to start at number 10 and count back four on the number line. One, two, three, four.

We started at 10. We counted back four. And we finished counting at number six. We subtracted four from 10 by counting back four. Counting back is the same as subtracting. Let’s practice what we’ve learned with some questions.

To find seven take away four, we can start at seven and count backward four. Seven, six, five, what, what. Finish counting backward to find the answer to seven take away four.

In this question, we have to find the answer to seven take away four. When we see the words “take away,” we know that that means subtract. We would write this as seven subtract four. The question also tells us to start at number seven and count backward four. We can see that some of the numbers have already been written. Seven, six, five. What comes next? If we start at seven and count backward, seven, six, five, the next number is four. Seven, six, five, four, three.

We started at seven. We counted backward or subtracted four. We finished counting at number three. To find seven take away four, we started at seven and counted backward four. Seven, six, five, four, three. The answer to seven take away four is three.

There were nine balls in a box. Then, five of them were removed. How many balls are left?

This is a word problem. Let’s look carefully at the information we’re given. To start with, we’re told that there are nine balls in a box. Then, five of them were removed. If the balls were removed, that means they were taken away. We have to work out how many balls are left.

Have you worked out what kind of problem this is? When we have a number of balls and we take some away, we need to subtract. So, there were nine balls in a box. And five were removed or taken away. To find out how many balls are left, we need to take away five from nine. Let’s use a number line to help us subtract.

We need to start at number nine because there were nine balls in the box at the start. We have to take away five. That means we need to count backward five starting at number nine. One, two, three, four, five. Nine, eight, seven, six, five, four. Nine take away five equals four. To help us subtract, we started at number nine on the number line and we counted back five. If there are nine balls in a box and five of them are removed, there will be four balls left. Nine subtract five equals four.

Count back to find nine take away four.

In this question, we have to use the number line to help us count back to find the answer to nine take away four. We need to start at number nine and count back four on the number line to find the answer. The jumps have already been drawn for us. We just need to start at nine and count back. Nine, eight, seven, six, five. Nine subtract four equals five. We used the number line to help us count back to subtract. Nine, eight, seven, six, five. Nine take away four equals five.

Write The subtraction equation. Is it six subtract one equals three, six subtract three equals three, six subtract three equals two, or six subtract four equals three?

In this question, we have to find the subtraction equation which matches the number line. Let’s look more closely at what’s happening on the number line. We started counting at number six. So, we know the starting number or the first number in our subtraction equation should be number six. But that doesn’t help us much because all of these subtraction equations start with the number six.

How many times did we count back on this number line from number six? There are three arrows, which must mean that we have to subtract three. One, two, three. If we count back three, that’s the same as subtracting three. Either of these two equations could be correct because both of these are subtracting three. Is six subtract three three? Or is six subtract three two?

Let’s start at six and count back three. Six, five, four, three. We finished counting at number three. The subtraction equation which matches the number line is six subtract three equals three. If we start at six on the number line and count back three, we will finish counting on number three. Six subtract three equals three.

What have we learned in this video? We have learned how to subtract by counting back on a number line.