Video Transcript
Adding Equal Groups
In this lesson, we’re going to
learn how to find the total number of objects in several equal groups. And we’re going to do this by using
skip counting or by using repeated addition.
Now, don’t panic, but it looks like
this video might have been invaded by a monster. No need to worry though; it looks
like he’s quite friendly. He’s an interesting looking
monster, though, isn’t he? He’s wearing some medals. There’s a group of one, two, three,
four, five, six, seven, eight, nine, 10 medals. Here’s another monster and
another. We can see three equal groups of
medals now because each monster has the same number. They have 10 medals each. How many medals are there
altogether? To find the answer, we need to add
together 10 and 10 and 10. Now, when we add the same number
over and over again, we’re repeating ourselves, aren’t we? We call this repeated addition.
What is 10 add 10 add 10? We know that 10 add 10 equals
20. And then if we add our last 10 to
20, we get a total of 30. 10 plus 10 plus 10 equals 30 medals
altogether. Now there’s a quicker way to add
equal groups together if we’re able to use it. Rather than working out lots of
additions one after the other, we could skip count. And because we know how to skip
count in 10s, this is a good way to find the answer. We’re going to need to count in 10s
three times: 10, 20, 30.
You know, if we were to label this
number line, we could show that, really, what we’ve done is just add 10 three
times. But because we know how to skip
count in 10s, it’s a lot quicker. 10, 20, 30. Three monsters with 10 medals makes
30 medals. Three groups of 10 are 30. Or we could just say three 10s are
30. We can use these skills of repeated
addition or skip counting to find the totals of any equal groups.
Let’s say we want to find out how
many ears the monsters have altogether. What would we do? We could see that each of the
monsters has one, two, three, four, five ears. And there are four monsters, so
this makes four equal groups of five. So we could find the answer by
using repeated addition. That means adding the number five
four times: five add five add five add five. Or if we know how to skip count in
fives, this would be quicker. We could make four jumps of
five.
What about if we wanted to find out
how many eyes we can see in total? Well, we can see that each of our
monsters has got two eyes. And because there are four
monsters, there are four equal groups of two. So what are the two ways we could
use to find the total? We could add two four times. Or if we know how to count in twos,
we could just skip count in twos four times. Let’s now answer some questions
where we have to use either repeated addition or skip counting to find the totals
when we add lots of equal groups together. Watch out; we may come across some
more monsters along the way.
Jacob has five fishbowls. There are three fish in each
bowl. How many fish does Jacob have?
In this question, we need to find
out how many fish Jacob has. Now we’re given a picture to help
us, so we could just count all the fish: one, two, three, and so on. But counting one by one like this
can take a while, and there are quicker ways we could find the answer. Let’s use the information that
we’re given to help us. To begin with, we’re told that
Jacob has five fishbowls: one, two, three, four, five. We’re then told that there are
three fish in each bowl. They’re easy to spot in each bowl
because they’re three different colors. Each bowl contains a yellow fish, a
red fish, and an orange fish. Every bowl has an equal group of
fish. In other words, each bowl contains
the same number of fish.
So, really, what this question is
asking us is five bowls of three fish is how many fish? Or five groups of three is
what? To find the answer, we could count
in threes, one for each fish bowl. Otherwise, we need to find the
answer to three plus three plus three plus three plus three. We know that three plus another
three makes six. And if we add another group of
three to six, we have seven, eight, nine. If we add another group of three to
nine, we have 10, 11, 12. That’s four groups of three or four
fish bowls that we’ve added. We just need to add one more lot of
three. 12 add another three is 13, 14,
15.
You know, if we knew how to skip
count in threes, we could have found the answer even quicker. Three, six, nine, 12, 15. Five bowls of three fish is 15
fish. Five groups of three is 15. The total number of fish that Jacob
has is 15.
A monster has five fingers on each
of its four hands. How many fingers does the monster
have altogether?
The word altogether in this
question means in total. Now, one way we could count the
total of the monster’s fingers is just one by one. One, two, three, four. This is taking quite a while, isn’t
it? There’s got to be a quicker way to
find the answer. Let’s look at the fact we’re given
in the first sentence.
We’re told that a monster has five
fingers on each of its four hands. We’ve already counted four of the
fingers, can you see? And then we add this one here that
looks a bit like a thumb; that makes five. And we can see that the monster has
four hands altogether. One, two, three, four. And because each of the monster’s
hands are the same, we know we can see five fingers plus another group of five
fingers plus another group and one more. We can see four equal groups of
five. So how could we find the total of
four groups of five?
Well, we know how to skip count in
fives, don’t we? It’s quite quick to do. Five, 10, 15, and so on. What if we counted in fives four
times, one for each of the monster’s hands? Each time we make a jump of five,
we’ll show it on a number line. Five, 10, 15, 20. Our monster has five fingers on
each of its four hands. And we found the total number of
fingers that the monster has altogether by skip counting in fives four times. Five, 10, 15, 20. The number of fingers that the
monster has altogether is 20.
There are four monsters. Each monster has two horns. How many horns are there? Two plus two plus two plus two
equals what. Each monster has five eyes. How many eyes are there? Five plus five plus five plus five
equals what. Each monster has 10 teeth. How many teeth are there?
And we can see an addition that has
four empty boxes. And we need to find the answer. So to begin within this problem,
we’re told that there are four monsters. And we should be pretty thankful
that we can’t see any pictures of these monsters because they sound pretty
scary. Each monster has two horns, five
eyes, and 10 teeth. And we need to use this information
to find the number of horns, the number of eyes, and the number of teeth.
So in the first part of the
question, we read that each monster has two horns. This means that there are one, two,
three, four groups of two horns. These are four equal groups because
we know that each monster has the same number of horns. That’s why we can see how to find
the answer here by adding the number two four times: two plus two plus two plus
two. We know that two plus another two
equals four. And if we add another two to four,
we get six. And finally, six plus another two
makes eight. There are eight horns
altogether.
Next, we’re told that each monster
has five eyes. So we know there are one, two,
three, four groups of five eyes. And, you know, because our four
groups are equal, we can again find the answer by adding the same number four
times. This time it’s five because there
are five eyes: five add five add another five add another five. Let’s get adding. To begin with, let’s add our first
two fives. Five add five equals 10. Now if we add our next group of
five, 10 plus five more is 15. And five more than 15 is 20. There are 20 eyes altogether.
In the final part of the question,
we’re told that each monster has 10 teeth. So we know what this means by now,
don’t we? It means there are four equal
groups of 10 that we need to count. And we can use this information to
complete our addition. To find the answer, we need to find
the total of 10 plus 10 plus another 10 plus one more 10. What we’re doing here is repeating
the same addition again and again, aren’t we? 10 plus another 10 equals two 10,
which is the same as 20. 20 plus one more 10 gives us a
number with three 10s in it; it’s 30. And 30 plus one more group of 10
makes four groups of 10, which is 40. There are 40 teeth altogether. Thankfully, they’re smiling.
We’ve added the same number four
times here to help us find each answer. We know that each monster has two
horns. And so to find the total number of
horns, we needed to add together two and two and another two and one more two. There are eight horns
altogether. Because each monster has five eyes,
we just needed to add together the number five four times. The total number of eyes is 20. And then finally, because we’re
told each monster has 10 teeth, this is the same as four equal groups of 10. We just added the number 10 four
times. The number of teeth there are
altogether is 40.
What have we learned in this
video? We’ve learned how to find the total
number of objects in several equal groups. We’ve done this by using repeated
addition or skip counting.
