Watch: Estimating and measuring
Fin and Snoot calculate the length of their new cars, using feet, centimeters and meters.
NARRATOR: Hello Snoot, what鈥檚 that you鈥檙e driving?
ALIEN: (Alien language)
NARRATOR: I see, you hired a go-kart from the intergalactic market.
Hello Finn.
ALIEN: (Alien language)
NARRATOR: What an impressive car. On Earth, that鈥檚 called a limousine. It鈥檚 a lot longer than Snoot鈥檚 go-kart isn鈥檛 it?
How long is it exactly?
ALIEN: Eh
NARRATOR: I鈥檝e got an idea, you can estimate the length in steps.
The go-kart is ten steps in length and the limousine is 30 steps in length.
30 is three times ten. That makes the limousine three times longer than the go-kart.
ALIEN: (Alien language)
NARRATOR: I know Snoot. Counting things out in steps isn鈥檛 very accurate, it just gives you an estimate of how long things are.
If you want to know exactly, you鈥檒l have to use a tape measure.
On Earth we use centimetres to measure quite small lengths, like the width of a tire, or the diameter of a wheel.
And we use metres to measure longer lengths, like the length of a car.
ALIENS: Ah ha!
NARRATOR: So, according to the tape measure, Snoot鈥檚 go-kart is two metres long, and Finn鈥檚 limousine is six metres long.
Six is three times two, so your estimates were right!
The limousine is three times longer than the go-kart.
Hello Plimble.
ALIEN: Hello.
NARRATOR: I see you hired a monster truck. I think we are going to need a bigger tape measure.
How can we measure length or height?
We can measure lengths or heights in different units.
- An insect might be measured in millimetres (mm).
- A book might be measured in centimetres (cm).
- A playground might be measured in metres (m).
- The distance to the shops might be measured in kilometres (km).
We can solve problems of length and height if we know the different units and how they are related.
Example 1
Five children have the following heights:
| Children | Height |
|---|---|
| Noah | 96 cm |
| Dessie | 90 cm |
| Layla | 120 cm |
| Carley | 115 cm |
| Bilal | 106 cm |
The children are all standing behind a wall which is 1 metre high. Whose head can be seen above the wall?
The measurement for the height of the wall is in metres, but the measurements for each child's height is in centimetres. So we need to convert the height of the wall from metres into centimetres.
1 metre = 100 cm
Look through the table again to see who is taller than 100 cm.
So, Layla, Carley and Bilal can be seen over the wall.
Example 2
The children's eyes are 10 cm below the top of their heads. The eye heights of the five children are shown in the table below:
| Children | Eye height |
|---|---|
| Noah | 86 cm |
| Dessie | 80 cm |
| Layla | 110 cm |
| Carley | 105 cm |
| Bilal | 96 cm |
Which of the children can see over the wall?
Remember the wall is 1 metre or 100 cm high. Look through the table above to see whose eyes are above this measurement.
You can see that Carley and Layla have measurements for eye height greater than 100 cm, so they can see over the wall.
Top tip
Convert all lengths into the same units to make the problem easier!
- Lengths can be in mm, cm, m or km.
- Heights are a type of length measured upwards.
Activity 1
My hand is 10 cm wide.
(i) How many hand-widths fit across a desk which is 120 cm wide?
(ii) How many hand-widths fit up a doorway which is 2 m high?
Activity 2
Practise solving problems involving length and height.
Try your best to answer all of the questions.
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