Video Transcript
Dividing by Eight
In this video, we’re going to learn
how to divide by eight using models, like arrays, and our knowledge of the eight
times table. When we’re learning to divide by
eight, it really helps to use the eight times table facts.
Let’s start by practicing the eight
times table. One times eight is eight, two
eights are 16, three times eight is 24, four times eight is 32, five eights are 40,
six times eight is 48, seven eights are 56, eight times eight is 64, nine eights are
72, 10 eights are 80, 11 eights are 88, and 12 eights are 96. We call these numbers multiples of
eight.
Let’s practice counting in eights
one more time. Another way to multiply by eight is
to skip count by eights. Eight, 16, 24, 32, 40, 48, 56, 64,
72, 80, 88, 96. Knowing the eight times table facts
will really help us in this lesson when we’re dividing by eight. When we’re dividing by eight, one
way to find the answer would be to divide 40 counters into groups of eight. Each of these groups contains eight
counters. So, when we’re thinking about
dividing by eight, we’re thinking about how many groups of eight there are or how
many eights are there in 40. And there are five groups of
eight.
One eight is eight, two eights are
16, three eights are 24, four eights are 32, five eights are 40. 40 divided by eight equals
five. There are five equal groups of
eight in our array. Which times table fact did we use
to help us find the answer? It was five times eight. If we know that five times eight is
40, we know that 40 divided by eight equals five.
So, we can use models, such as our
array, and our knowledge of the eight times table to help us divide by eight. Now that we’ve learned two ways to
divide by eight, let’s try some questions.
Use the following diagram to
calculate 56 divided by eight.
In this question, we’ve been shown
a diagram or a model to help us calculate 56 divided by eight. We could call this diagram an
array. An array is when we organize
objects into equal groups. We know there are 56 balloons
altogether, and we have to divide those 56 balloons by eight. The divisor, or the number we’re
dividing by, is the number eight. We’re being asked how many eights
there are in the number 56. So, the array shows us that 56
balloons are ranged into equal groups or rows of eight.
The balloons have been divided into
groups of eight. How many equal groups or rows of
eight balloons are there? In other words, how many eighths
are there in 56? Let’s count them. Here’s one, two, three, four, five,
six, seven. If we have 56 balloons and we
divide them into equal groups of eight, there are seven groups. 56 divided by eight equals
seven. We used the array to help us
calculate 56 divided by eight.
This robot divides any number by
eight and gives a result. In this case, the number 16 gives a
result of two as 16 divided by eight equals two. What will the result be in the
following case? 40 divided by eight equals
what. And what will the result be in the
following case? 64 divided by eight equals
what.
In the first part of this question,
we have to help the robot calculate 40 divided by eight. And in the second part of the
question, we have to help the robot calculate 64 divided by eight. Did you notice that in all of the
calculations we’re dividing by eight? How could we calculate 40 divided
by eight? We could use an array and our
knowledge of the eight times table to help.
When we’re dividing by eight, we
can think of this as dividing a number into equal groups of eight. Here’s one group of eight, which
gives us a total of eight. Two eights make 16. Three eights make 24. Eight, 16, 24. Four eights are 32, and five eights
make 40. Eight, 16, 24, 32, 40. So, if the number 40 goes in and
the robot divides it by eight, the result will be five. There are five eights in 40. 40 divided by eight equals
five.
Now, we just need to answer the
second part of the question. What is 64 divided by eight? How many eights are there in
64? Let’s keep on counting in
eights. We already know that five groups of
eight makes 40, so let’s just keep counting forward in eights. Five eights are 40, six eights are
48, seven eights are 56, and eight eights are 64. There are eight eights in 64. If we put the number 64 into the
robot and he divides it by eight, the result will be eight because 64 divided by
eight equals eight.
40 divided by eight equals five and
64 divided by eight equals eight. We found the results using arrays
and our knowledge of the eight times table.
Jacob says that 32 divided by eight
is four, and David says that 32 divided by eight is five. Who is right?
This question is all about dividing
by eight. Jacob thinks that 32 divided by
eight is four, and David thinks that 32 divided by eight is five. Who is correct? To help us work out the correct
answer to 32 divided by eight, we could use our knowledge of the eight times
table. One times eight is eight, two times
eight is 16, three times eight is 24, and four times eight is 32. So, who is correct? It’s Jacob. If four times eight is 32, that
means that there are four eights in 32. 32 divided by eight is four. So, Jacob is right. 32 divided by eight equals
four.
We used our knowledge of the eight
times table to help us divide by eight.
What have we learned in this
video? We have learned how to divide by
eight using arrays. We also learned how to use the
eight times table to divide by eight.
