The tallest building in the world, the Burj Khalifa in Dubai, is 828 metres tall. A model of the building is made using the ratio 1 : 5,000.
How high is the model in centimeters?

A

1,656 cm

B

165.6 cm

C

16.56 cm

D

1.656 cm

Don't guess the answer

Height of the model = 828 m ÷ 5,000 

                                 = 82,800 cm ÷ 5,000 
                                 = 16.56 cm

Because the angles are along a straight line we know they must add up to 180°.

So we must divide 180° in the ratio 4 : 11

4 + 11 = 15

∠AOB will be 4/15, and ∠BOC will be 11/15 of the full 180°

So: ∠AOB = 4/15 × 180° = 4 × 12° = 48°

And: ∠BOC = 11/15 × 180° = 11 × 12° = 132°

(Check: 48° + 132° = 180°)

We need to divide 90° in the ratio 2 : 3

2 + 3 = 5

So
∠AOB = (2/5) × 90° = 36°
and 
∠BOC = (3/5) × 90° = 54°

Question 10

Ratios (Grade 8, General)

Help

AOC is a straight line and the ratio of the angles is:

∠AOB : ∠BOC = 4 : 11

What is the size of angle AOB?

A

40°

B

48°

C

60°

D

132°

This is NOT a TEST ... it is just you learning.

Help

∠AOC is a right angle and the ratio ∠AOB : ∠BOC = 2 : 3

What is the size of angle BOC?

A

36°

B

45°

C

54°

D

60°