Video Transcript
Subtracting Numbers up to 20 on a Number Line
In this video, we will learn how to subtract within 20 by jumping backward in ones on a number line.
We can use a number line to help us subtract. To subtract three from 12, we would need to start at number 12 on our number line and count backward three spaces. One, two, three. We landed on number nine. 12 subtract three equals nine.
To subtract using a number line, we started at number 12. We jumped backward three spaces on the number line. We landed on number nine. The difference between 12 and three is nine. Let’s practice subtracting on a number line with some example questions.
Count back to subtract. Find the difference.
In this question, we’re being asked to subtract five from 12. We’re told to count back to subtract. So, we can use the number line to help. We’re starting with 12, so we can start at number 12 on our number line. The amount we’re subtracting is five. So, if we start at 12 and count backward five, we will find the difference.
We have to count back five to subtract five. One, two, three, four, five. 12 take away five is seven. We started at 12. We counted backward five. We landed on number seven.
Fill in the missing number. 12 subtract five equals what? Use the number line if you need to.
In this question, we start with 12. So, we could start at 12 on our number line. We have to subtract five. This means we need to count backward five spaces on the number line. One, two, three, four, five. We landed on number seven. If we start at 12 and subtract five, we will get seven. We used the number line to help us subtract. 12 subtract five equals seven.
Fill in the missing number. What subtract 11 equals four? Use the number line if you need to.
We’re shown a subtraction sentence. We don’t know how many there are at the start. We do know that we have to subtract 11. And the answer is four. If we end up at number four and we’ve subtracted 11, we could count forward from number four 11 spaces on the number line. This will take us back to the number we started at.
One, two, three, four, five, six, seven, eight, nine, 10, 11. We started with number 15. If we start at 15 and subtract 11, we will land on number four. The missing number is 15. The difference between 15 and four is 11. We can find the difference by counting backward or counting forward. The missing number in this equation is number 15.
What have we learned in this video? We’ve learned that we can subtract by counting backwards on a number line. We also learned that we can find the difference by counting forward on a number line.
