Unit 19 Section 2 : Plans
In this section we look at plans drawn to a particular scale.
A scale is used to represent real life measurements on the smaller plan.
Converting measurements
In the example below, we see how to work out "real life" measurements from a plan.

On the left is the plan for a room. The scale for this plan is 1 : 200.
This means that 1 cm on the plan represents 200 cm (or 2 m) in real life.
To work out the dimensions of the room in real life, we need to measure the room on the plan.
The room measures 3 cm by 2 cm.
Because the scale is 1 : 200, the real life measurements will be 200 times larger.
The length of the room in real life must be 3 cm × 200 = 600 cm or 6 m
The width of the room in real life must be 2 cm × 200 = 400 cm or 4 m

Perimeters and Areas
When working out perimeters and areas, it is best to convert to the "real life" measurements first, and then do the calculations.
In the plan above, we worked out that the "real life" dimensions of the room are 6 m by 4 m.
The perimeter of this room must be 6 m + 4 m + 6 m + 4 m = 20 m.
The area of this room must be 6 m × 4 m = 24 m².
Example Question
Below is the plan of a village hall. The scale of the plan is 1 : 100. Use the plan to answer the questions below.
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.
Remember that 1 cm on each plan is the same as the length of 2 small squares.
You have now completed Unit 19 Section 2
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Produced by A.J.Reynolds January 2001