Lesson Video: One More and One Less: Numbers up to 20 Mathematics • 1st Grade

In this video, we will learn how to find one more or one less than numbers between 10 and 20 by using place value blocks.

09:03

Video Transcript

One More and One Less: Numbers up to 20

In this video, we will learn how to find one more or one less the numbers between 10 and 20 using place value blocks. In this video, we’re learning how to find one more or one less the numbers between 10 and 20. Here we have a group of 10 blocks. How could we find one more than 10? One way we could find one more than 10 is to add one more brick. One more than 10 is 11. 10 and one more makes 11. Another way we could find one more than 10 is to start at 10 on our number line and count forward one place. One more than 10 is 11. One more than 11 is 12. 10 and two makes 12. One more than 12 is 13. 10 and three makes 13. One more than 13 is 14. We can keep on adding one more until we reach 20.

We’ve learned that to find one more than a number, we can use blocks to help. To find one more, we add one more block or we count forward one place on the number line. So how could we find one less than a number? How could we find one less than 20? If we take away one from 20, we’re left with a 10 and nine ones. 10 and nine makes 19, so we can say that one less than 20 is 19. We could also start at 20 on our number line and count back one space. One less than 20 is 19. And to find one less than 19, we can take away one and count back one on the number line. 10 and eight makes 18, so one less than 19 is 18.

So far, we’ve learned to find one more; we need to add one block or count forward one space on the number line. We’ve also learned that to find one less than a number, we need to take away one block or count back one on the number line. Let’s put into practice what we’ve learned now with some questions.

Write the number of apples that is one less than the given number of apples.

In this question, we’re shown an amount of apples, but we’re not told how many apples there are. So first, we’ll need to count them, one, two, three, four, five, six, seven, eight, nine, 10, 11, 12, 13. Now that we know there are 13 apples, we can find one less. How could we find one less than 13? To find one less than 13, we just need to take one apple away. Now, there are only 12 apples. One less than 13 is 12. We were given 13 apples, and we were asked to find one less. So we took one apple away, and we started at 13 on our number line and counted back one. One less than 13 is 12.

Think about finding one more. What is one more than two? What is one more than 12?

This question is all about finding one more. We have to find one more than two and one more than 12. How could we find one more than two? We would just need to add one more block. Two add one equals three. One more than two is three. We can do the same to find one more than 12. One more than 12 is 13. 12 plus one equals 13. To find one more than two, we added one more brick. Two and one more is three. 12 and one more is 13.

Michael has shown that 14 is one ten and four ones. To find one less, he can take away a one. Fill in the blank: One less than 14 is one ten and what ones. Fill in the blank: One less than 14 is what.

In this question, we’re told that Michael has made the number 14. He made the number 14 using one ten and four ones. He’s trying to find one less than 14, and we’re told he can do this by taking away a one. So let’s take away one of Michael’s four ones. One less than 14 is one ten and three ones. Now, let’s complete the second sentence. One less than 14 is what. If one ten and four ones is 14, then one ten and three ones is 13. Michael made the number 14 using one ten and four ones. We had to find one less, so we took away a one. Michael was left with one ten and three ones. One less than 14 is 13.

What number is one more than 10 plus seven?

This question is all about finding one more. We have to find one more than 10 plus seven, and we’ve been given a model to help. The model shows a one ten and seven ones. We need to add these together. What does 10 add seven make? 17. One ten and seven ones make 17. To find one more than 17, we just need to add another one. Instead of finding 10 plus seven ones, we need to find 10 plus eight ones. One ten and eight ones makes 18. 10 plus seven is 17. 10 plus eight is 18. One more than 10 plus seven is 18.

What have we learned in this video? We’ve learned that we can find one more by adding a ones block to a number or by counting forward one place on a number line. We’ve also learned that we can find one less than a number by taking away a ones block or by counting back one. Finding one more is the same as adding one, and finding one less is the same as taking away one.

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