### 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.