Video Transcript
Comparing Three-Digit Numbers Using
Number Lines
In this video, we will learn how to
use number lines to compare three-digit numbers.
The number 675 is a three-digit
number. We use the position of each digit
to tell us its value. The six digit in the number 675 is
worth six 100s. The seven digit is worth seven
10s. And the five digit is worth five
ones. We use the value of each digit in a
three-digit number to help us compare three-digit numbers.
These monsters are going to have a
race. Each monster has been given a
three-digit number for the race. But the monsters have lined up in
the wrong order. 156, 153, 154, 159, 150, 151, 158,
160, 152, 155, 157. Let’s help the monsters line up in
the correct order. When we count on a number line, we
start with the smallest number. And we read from left to right. As we count from left to right, the
numbers should increase by one each time.
Which of the monsters is wearing
the shirt with the smallest three-digit number? The first number is 156. If we write this number into our
place value chart, we can see it has one hundred, five tens, and six ones. The number 153 also has one hundred
and five tens but only three ones. Did you notice that, so far, all of
our three-digit numbers have had one hundred and five tens? 154 has four ones. The only digit that’s changing is
the ones digit. 159 has one hundred, five tens, and
nine ones. The number 150 has no ones. So far, this is the smallest number
because all of the three-digit numbers have had one hundred, five tens, and some
ones.
151 has one in the ones place. The number 160 has one hundred and
six tens. This is the greatest number so
far. Now we know that number 150 is the
smallest, we can place it at the beginning of our number line. And we know that the number 160 is
the largest number because it has six tens and all the other numbers only have five
tens. Now we know that all of the
monsters need to line up between the numbers 150 and 160.
Did you notice that both of these
numbers end in a zero? They’re both multiples of 10. This is the halfway mark on the
number line. Which number comes halfway between
150 and 160? It’s the number 155. Which number comes after 150? It’s the number 151, 152, 153. The number which comes after 153
but before 155 is the number 154. Which number comes after 155? 156, 157, 158, and the number which
comes after 158 but before 160 is 159. We placed the monsters in the
correct position on the number line. 150, 151, 152, 153, 154, 155, 156,
157, 158, 159, 160.
To help us order the numbers, we
used our place value chart to help. We compared the value of the digits
in the three-digit numbers, and we placed the smallest and the largest numbers on
the number line. We placed the number which is
halfway between the smallest and largest numbers next on the number line. Then we counted forward in ones to
place the other monsters on the number line. In this video, we’re going to use
our knowledge of place value to help us compare three-digit numbers. Let’s try some practice
questions.
Olivia and Amelia are comparing
numbers to the right and to the left of 322 on a number line. Who is correct? The numbers to the right of 322 are
greater than 322 or the numbers to the left of 322 are greater than 322.
Here’s the number 322 on both of
the number lines we’re given. On the first number line, the
numbers to the right of 322 have been circled orange. And the girl says that these
numbers are greater than 322. Is she correct? The first number to the right of
322 is 323. Is 323 less than or greater than
322? Let’s compare the ones digits. 322 has two ones. 323 has three ones. And we know that three is greater
than two. 324 is greater than 323. 325 is greater than 324. 326, 327. When we count to the right on the
number line, the numbers increase by one each time. So the numbers to the right of 322
are greater than 322.
The numbers to the left of the
number 322 are less than 322. 321, 320, 319, 318, 317. The numbers are decreasing by one
each time. Each time we count to the left,
we’re taking away one. The numbers to the right of 322 are
greater than 322.
Which number sentence is
correct? 225 is equal to 240. 225 is less than 240. 225 is greater than 240.
We need to use the number line to
help us decide which number sentence is correct. We’re being asked to compare the
numbers 225 and 240. We know that 225 is not equal to
240 because the numbers are in different places on the number line. If they were equal, the numbers
would be in the same position on the number line. Is 225 less than 240? The number 225 is to the left of
240 on the number line. Let’s start at 240 and count back
to 225. Watch what happens to the numbers
as we count back. 240, 235, 230, 225. The numbers were going down by five
each time. We’re taking away five each time we
count to the left. If the numbers are getting smaller,
that means that 225 is less than 240.
We know that 225 is not greater
than 240. The numbers to the right of 240 are
greater than 240. And 225 is to the left. The number sentence which is
correct is 225 is less than 240.
Compare the two numbers. 836 what 843. Which symbol should go between
them? Hint: Use the number line to help
you.
We’re being asked to use the
correct symbol to compare these two numbers. Is 836 less than 843? Are the two numbers equal? Or is 836 greater than 843? In this question, we’re told to use
the number line to help. Where would we place the number
836? We know it comes after 830 but
before the number 840. 836 only has three tens not
four. The number 835 is halfway between
830 and 840. And we know that 836 is one more
than 835. So the number 836 would go around
here on the number line.
Where should we place 843? The four digit is worth four 10s in
843. So 843 comes between 840 and
850. It’s after 840 but before 850. The halfway mark would be 845. We know that three is less than
five, so 843 would come before 845. Now we can see that 843 is greater
than 836, so 836 is less than 843. The symbol which should go between
the two numbers is “less than” because 836 is less than 843.
What have we learned in this
video? We’ve learned how to compare
three-digit numbers using a number line. We’ve learned that when we count on
or count forwards, the numbers increase. And when we count to the left or we
count back on a number line, the numbers get smaller or decrease.
