# Lesson Video: Two-Digit Numbers on a Number Line Mathematics • 1st Grade

In this video, we will learn how to represent numbers from 0 to 100 on number lines.

06:22

### Video Transcript

Two-Digit Numbers on a Number Line

In this video, we will learn how to represent numbers up to 100 on a number line.

We can use number lines to help us find or locate numbers. Where would number 23 go on this number line? We can see the number line starts at 10. And the next number which is marked on the number line is number 20. We need to find number 23, which comes after number 20. The number after 20 is number 21. The number after 21 is 22. And number 23 comes after number 22. We located number 23 on the number line. We realize the number line started at number 10, and the number 20 was the next number marked on the number line. We knew the number 23 comes after 20. So we counted forward in ones until we reached number 23. We can also use number lines to help us find the missing number. Which number comes after 16 but before 18? It’s number 17.

Number lines don’t always go up in ones. Sometimes the gap between each number is more than one. This number line starts at zero and ends at 100. Watch what happens if we count in ones. Zero, one, two, three, four, five, six, seven, eight, nine, 100. That’s not right. We’re not counting in ones on this number line. What if we count in 10s? Zero, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100. On this number line, we’re counting in 10s.

Can you find the missing number? Which number comes after 60 if we’re counting in 10s? Our missing number also comes before 80 if we’re counting back in 10s. The missing number is 70. 10, 20, 30, 40, 50, 60, 70.

Let’s recap what we’ve learned. Number lines can go up in ones. And we’ve also learned that number lines can go up in 10s. Zero, 10, 20, 30, 40, 50, 60, 70, 80. Let’s use what we’ve learned to help us locate numbers up to 100 on a number line.

What is the missing number?

We’re shown a number line. It starts at number 12 and ends at number 22. We have to find the missing number. We know the gap between the numbers is one. We’re counting in ones on this number line. 12, 13, 14, 15. Which number comes after 15? It’s number 16. The missing number is 16. We found the number by counting in ones from number 12 on the number line.

What is the number that is one more than 44?

We’re shown a number line. And we’re told to use it to help us find the number which is one more than 44. Here’s the number 44 on the number line. Which number is one more? We need to count forward one on the number line. The number one more than 44 is 45.

Which label represents the number 70? Is it A, B, or C?

We don’t know which numbers are represented by A, B, and C. But the numbers that we can see — 20, 40, and 60 — are all multiples of 10. Which number is 10 more than 20? 10 more than 20 is 30. So we know that A represents the number 30. Let’s keep counting forward in 10s. 40, 50. So we know that B is 50. The next number is 60. And 10 more than 60 is 70. So C is 70. So the label which represents the number 70 is C. On this number line, we’re counting in 10s. 20, 30, 40, 50, 60, 70. The label C represents the number 70.

What have we learned in this video? We’ve learned how to represent numbers up to 100 on a number line.