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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:

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Question

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° ... ... ...
  1. Are the number of spokes and the angles formed between the pairs of consecutive spokes in inverse proportion?
  2. Calculate the angle between a pair of consecutive spokes on a wheel with 15 spokes.
  3. How many spokes would be needed if the angle between a pair of consecutive spokes is 40°?
Sum
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Solution

  • Number of sticks = 8
    The angle between each pair of consecutive spokes = `360/8`
    = 45°
  • Number of sticks = 10
    The angle between each pair of consecutive spokes = `360/10`
    = 36°
  • Number of sticks = 12 The angle between each pair of consecutive spokes is `360/12`
    = 30°
Number of spokes 4 6 8 10 12
Angle between a pair
of consecutive spokes
90° 60° 45° 36° 30°

According to the question:

  1. Yes, the number of spokes and the angle between any pair of consecutive spokes are inversely proportional.
  2. Number of sticks = 15
    Angle between each pair of consecutive spokes = `360/15`
    = 24°
  3. Given angle between each pair of consecutive spokes = 40°
    number of sticks required will be = `360/40`
    = 9
    Hence, number of sticks required = 9
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Chapter 11: Direct and Inverse Proportions - EXERCISE 11.2 [Page 141]

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NCERT Mathematics [English] Class 8
Chapter 11 Direct and Inverse Proportions
EXERCISE 11.2 | Q 3. | Page 141

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