Wednesday, 15 September 2021 09:03

## Scale Drawing - Class 8 Mathematics Revision Notes

Scale Drawing

Worked Exercise

1. The distance between two villages is 6.4KM. On the map of the region this distance is represented by a line 1.6 cm long. What is the scale of the map?
1. 1: 400000
2. 1: 40000
3. 1: 4000
4. 1: 4
Working
Actual distance = 6.4 km
Drawing length = 1.6cm
1 cm on the map = 6.4/1.6
= 4km on the ground
But 1 km = (1000 x 100) cm
4km = 4 x 1000 x 100
= 400000cm
Therefore scale = 1: 400000
The correct answer is A (1: 400000)
2. A rectangular field measures 105 m. On a scale drawing of the field, the longer side is 7cm.What is the measurement of the width on this scale drawing?
1. 5 cm
2. 50 cm
3. 500 cm
4. 7.35cm
Working
7 cm represents 105 m
1 cm represents (105 ÷ 7)
Scale used,
1 cm represents 15m
?                  75m
= (75 x 1)/15
5cm
The correct answer is 5cm (A)
3. The scale on a plan is 1:20. How many cm will represent 1m on this plan?
1. 50 cm
2. 50 cm
3. 5 cm
4. 2 cm
Working
1 : 20 scale means 1 cm on a drawing represents 20 cm on the ground.
1 cm represents 20cm
?                      100cm
=100/20
= 5cm
The correct answer is C (5cm)
4. A rectangular field measuring 720m by 550m is to be represented on a scale drawing using the scale 1: 10,000. What is the perimeter of the drawing in centimetres?
1. 0.254
2. 2.54
3. 25.4
4. 254
Working
1: 10000 means 1 cm on the map represents 10000 cm on the ground
If 1 cm = 10,0000cm
? = 72,000cm
= (72000/10000) cm
= 7.2cm
If 1cm = 10,000cm
= 55,000cm
= ( 55,000/10,000 ) cm
= 5.5cm
Perimeter P = 2(L+W)
= 2 (7.2 + 5.5)
= 25.4 cm
5. The scale of a map is 1: 50000. What is the length of this map of a road 20km long?
1. 40cm
2. 400 cm
3. 4000 cm
4. 4 cm
Working
Scale 1 : 50000 means 1cm on the map represents 50000 cm on the ground.
20 km = 20 x 1000 x 100
= 2000000 cm
50,000cm represents = 1 cm
2,000,000 represents = 2,000,000 ÷ 50,000
= 40cm
The correct answer is A (40 cm)