Find Half of a Shape, Quantity or Length

In this activity, we will be solving different problems for finding a half. 
 

Below are examples to show all the types of questions that may come up. 

 

1. Finding half of a shape 

Here we have a selection of shapes. Which of the shapes have been split in half?

 

  

 

To answer this we must remember what it means to find a half. 

 

A half is when something is shared into two equal parts. To find which shapes have been split in half, we need to look for which shapes have been split into two parts that are exactly the same size. To be equal they must be exactly the same. 

 

Let's look at each shape:

 

A: Here we have one part much bigger than the other, so this has not been split in half as the parts are not equal. 

B: If we turn our head or the screen, we can see that each part of this circle is exactly the same size - this one has been split in half. 

C: The parts are equal here, so this one has also been split in half. 

D: Just like shape A, we can see that one part is much bigger than the other, so this has not been split in half. 

E: We have to look closely at this one, but each part is equal, so this has been split in half. 

 

 

2. Finding half of a quantity

Here we have 20 pencils. What is half of 20 pencils?

 

  

 

We know that to find half we have to share the objects into two equal groups, so let's split these pencils into two equal groups!

 

Now, you cannot move these pencils on the screen, so grab a piece of paper and draw them!

First, draw out 20 pencils, these can just be little lines like this:

 

  

Now draw two circles to share the pencils into and start sharing them out between 2 groups, crossing off the lines as you go:

 

  

  

 

Continue doing this until all 20 lines have been crossed off and shared equally between the circles:

 

 

 

To check they have been shared out equally, we need to count how many are in each circle.

There are ten in each circle. 

As this is the same number, we know that they have been shared out equally. 

This means that half of 20 pencils is ten pencils!

 

3. Word problems for finding half 

Class 1J was growing sunflowers. The tallest sunflower grew to 20 cm. 

The smallest one was half the height of the tallest one. 

How tall was the smallest sunflower?

 

  

 

Let's have a look at how to answer this question. 

 

So we know that the smallest flower is half the size of the tallest flower. We know that the tallest flower is 20 cm. 

This means that we need to find half of 20 cm. 

So we need to split 20 equally into two groups to find half. So we can repeat what we did above with the pencils. 

Or another way to work this out is to divide 20 by 2, which is 20 ÷ 2 =

 

We can work this out by counting in 2s until we reach 20 and we see how many 2s we had to count to reach 20:

2, 4, 6, 8, 10, 12, 14, 16, 18, 20 - that took 10 sets of 2.

So 20 ÷ 2 = 10 or half of 20 is 10.

This means that the smallest sunflower was 10 cm!

 

Wow, that was a lot to take in!  Are you ready to tackle these questions?