Rehman is making a wheel using spokes. He wants to fix equal spokes in such a way that the angles between any pair of consecutive spokes are equal.
Rehman is making a wheel using spokes. He wants to fix equal spokes in such a way that the angles between any pair of consecutive spokes are equal. Help him by completing the following table.
| Number of spokes | 4 | 6 | 8 | 10 | 12 |
| Angle between a pair of consecutive spokes | 90° | 60° | .. | .. | .. |
(i) Are the number of spokes and the angles formed between the pairs of consecutive spokes in inverse proportion?
(ii) Calculate the angle between a pair of consecutive spokes on a wheel with 15 spokes.
(iii) How many spokes would be needed, if the angle between a pair of consecutive spokes is 40°?
1 Answers
A table of the given information is as follows
| Number of spokes | 4 | 6 | 8 | 10 | 12 |
| Angle between a pair of consecutive spokes | 90° | 60° | x1 | x2 | x3 |
From the given table, we obtain
4 × 90° = 360° = 6 × 60°
Thus, the number of spokes and the angle between a pair of consecutive spokes are inversely proportional to each other. Therefore, 4 × 90° = x1 × 8
similarly, x1 = (4 x 90°)/8 = 45°,
x2 = (4 x 90°)/10 = 36° and
x3 = (4 x 90°)/12 = 30°
Thus, the following table is obtained.
| Number of spokes | 4 | 6 | 8 | 10 | 12 |
| Angle between a pair of consecutive spokes | 90° | 60° | 45° | 36° | 30° |
(i) Yes, the number of spokes and the angles formed between the pairs of consecutive spokes are in inverse proportion.
(ii)Let the angle between a pair of consecutive spokes on a wheel with 15 spokes be
x. Therefore,
4 × 90° = 15 × x
x = (4 x90°)/15 = 24°
Hence, the angle between a pair of consecutive spokes of a wheel, which has 15 spokes in it, is 24°.
(iii) Let the number of spokes in a wheel, which has 40º angles between a pair of consecutive spokes, be y.
Therefore,
4 × 90° = y × 40°
y = (4x90)/40 = 9
Hence, the number of spokes in such a wheel is 9.