# Unit 17 Section 1 : Estimating metric units

It is very useful to be able to estimate lengths, masses, etc. because it may not always be easy to measure them.

Some useful hints for estimating are listed below:
 The height of a standard door is about 2 m. The length of an adult pace is about 1 m. The length of a size 8 shoe is about 30 cm. Most adults are between 1.5 m and 1.8 m in height. It takes about 15 minutes to walk one kilometre. The mass of a standard bag of sugar is 1 kg. The mass of a family car is about 1 tonne. 1 hectare = 10 000 m2 (about 2 football pitches). A teaspoon holds about 5 ml of liquid. The volume of a normal can of drink is about 330 cm3.
Sometimes you can estimate by comparing one thing where you know the size with another where you don't.

## Example Questions

Example Question 1
The picture below shows a tall man next to the front of a factory.

(a) Estimate the height of the factory in metres.
A tall man will probably be about 1.8 metres high.
We can see how many times taller the factory is than the man using the diagram below:

The factory is about five times as high as the man, so we multiply 1.8 metres by 5.

1.8m × 5 = 9m, so the height of the factory is about 9 metres.

(b) Estimate the height of the factory door in metres.
The door is taller than the man, but not twice as tall.
It is probably about 1½ times as tall, so we multiply 1.8 metres by 1½.

1.8m × 1½ = 2.7m, so the height of the factory door is a bit less than 3 metres.

Example Question 2
The picture below shows a car overtaking a lorry.

The car is 4.2 metres long and 2 metres high.

(b) Estimate the height of the lorry in metres.
The lorry is about three times taller than the car, so we multiply 2 metres by 3.
2m × 3 = 6m, so the height of the lorry is about 6 metres.

(b) Estimate the length of the lorry in metres.
The lorry is about twice as long as the car, so we multiply 4.2 metres by 2.
4.2m × 2 = 8.4m, so the length of the lorry is about 8½ metres.

## Exercises

Work out the answers to the questions below and fill in the boxes. Click on the button to find out whether you have answered correctly. If you are right then will appear and you should move on to the next question. If appears then your answer is wrong. Click on to clear your original answer and have another go. If you can't work out the right answer then click on to see the answer.

Question 1
Estimate the following:
 (a) the height of a football goal m (b) the width of a hockey pitch m (c) the width of a football goal m (d) the height of a netball post m
Question 2
Estimate the lengths of the following vehicles:
 (a) a car m (b) a bus m (c) an articulated lorry m (d) a motorcycle m
Question 3
Estimate the mass of the following:
 (a) a table tennis ball grams (b) a chair kg (c) a large dog kg (d) a pen grams (e) a calculator grams
Question 4
Estimate the volume of milk you would:
 (a) add to a cup of tea ml (b) pour on to cereal in a bowl ml (c) pour into a mug ml
Question 5
Estimate the volume of:
 (a) a football cm3 (b) a tennis ball cm3 (c) a table tennis ball cm3 (d) a hockey ball cm3
Question 6
Which of the following would be the best estimate for the mass of an apple:

Question 7
Which of the following would be the best estimate for the diameter of a saucer:

Question 8
Which of the following would be the best estimate for the capacity of a tea cup:

You have now completed Unit 17 Section 1
 Your overall score for this section is Correct Answers You answered questions correctly out of the questions in this section. Incorrect Answers There were questions where you used the Tell Me button. There were questions with wrong answers. There were questions you didn't attempt.
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