To understands what scale drawings are.

To be able to draw scale drawingsTo understand scale drawings.

What are scale drawings?Scale drawings are everywhere!

Scale Drawings

On Maps

Footprints of houses

Vehicle design

Can you think of any more?

Scale drawings are SIMILAR to the original.To say that two objects are SIMILAR means that they are identical in shape, but not in size. In order for two shapes to be similar they must have the same angles and the sides must be in the same ratio.

Example: Are these two shapes similar? Angles the

same

x2

x2

x2

x2Sides have the same ratio – x2

The two shapes are similar

Are these pairs of shapes similar?

3cm9cm

2cm

6cm

40°40°

50° 50°

5m

6m4m

10m

2m

3m

1m

1.5m50°

60°

70°

All scale drawings must have a scale written on them. Scales are usually expressed as ratios.Normally for maps and buildings the ratio:

Drawing length: Actual length

For maps the ratio is normally in the ratio:Map distance: Actual Distance

Example: 1cm : 100cm

The ratio 1cm:100cm means that for every 1cm on the scale drawing the length will be 100cm in real life

Example: 1:10000

The ratio 1:10000 means that the real distance is 10000 times the length of one unit on the map or drawing.

When you write a scale you must make sure that the units are the same.ExampleSimplify the scale 5cm to 1m

5cm:1m5cm:100cm1cm:20cm

Convert to the same

unitsAll ratios must be in the

form 1:n. To make cm 1cm then we must divide each

side by 5

Questions – Simplify the following scales

1)10cm: 2m2)5mm:10cm3)1cm:1km

1cm:20cm1mm:20mm1cm:100000c

m

Task• Make a scale drawing of the building which you are renovating. To do this you need to measure EVERY room and the outside of the building. Do this in metres.

• After you have measured the building you need to decide on a scale. Remember the whole drawing needs to fit on an A3 piece of paper.

(I advise you use the scale 1cm:100cm)

Using the scale 1cm:100cmIf a rectangular room measures 2.5m by 4m then you have to convert both of the lengths into cm. (as this is the unit in the scale)

2.5m = 250cm, 4m = 400cmIf 100cm in the actual drawing is represented by 1cm then to get from the actual to the scale you need to divide by 100.

250cm ÷ 100 = 2.5cm 400cm ÷ 100 = 4cmOn the scale drawing this room would be 2.5cm by 4cm