1. A STORY ABOUT DOUBLING

2. Mrs Hippo has lost all the little hippos from
her class. She is very forgetful teacher.
She doesn’t remember how many little hippos
belong in her class.
Before we start looking, can we help Mrs
Hippo work out how many little hippos are in
her class?

3. Mrs Hippo thinks and thinks and then she
remembers!
There were 8 groups of little hippos.
There were 3 little hippos in each group.
We know that each group of little hippos is the
same, so we can add all the groups together.

4. Let’s look at the first group of little hippos.
How many hippos can you see?
We can see three little hippos standing
together.

5. Look! More little hippos have joined the first
group.
How many little hippos are in this group?
There are three more little hippos. We have two
groups of three hippos in each group.
Put your thinking caps on to work out how many
little hippos altogether.
How could we easily work it out?
We can double the number in each group, so
double 3 is 6.
This means 3 by 2 is 6. We have found six hippos.

6. Look, some more little hippos have joined
their friends. How many more little hippos can
you see?
There are two more groups of three, so there
are six more little hippos.
Put your thinking caps on to work out how
many little hippos altogether.
Now we have four groups, with three hippos in
each group, so we can double and then double
again. If double 3 is 6, 3 multiplied by 4 means
double 6, which equals 12.
So 3 by 4 is 12. We have found 12 hippos now.

7. We have found lots more little hippos.
How could we easily work it out how many
now?
Remember we don’t need to count each one!
Now we have eight groups, with three hippos
in each group.

8. To work out how many little hippos altogether
we can double, double and then double again.
We start with our first group of three little
hippos.

9. We double the group of three.
Double 3 is 6.

10. We double again.
Double 6 is 12.

11. Finally we double, double, double.
So double 12 is 24.
Altogether we can see 24 little hippos.
8 groups of 3 makes 24.
This story about doubling showed us special
strategy where we can double, double, double
when there are eight groups of equal numbers.