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Solution


Q.

A brooch is a small piece of jewelry that features a pin on the back, allowing it to be fastened to a dress, blouse, or coat. Below are designs for some brooches.

Design A: Brooch A is crafted from silver wire in the shape of a circle with a diameter of 28 mm. The wire is also used to create 4 diameters, dividing the circle into 8 equal parts.

Design B: Brooch B is made with two colors, gold and silver. The outer portion is made of gold. The circumference of the silver section is 44 mm, and the gold section is uniformly 3 mm wide.

Based on the above information answer the following questions:

 

(iii) (b) A boy is playing with brooch B. He makes revolutions with it along its edge. How many complete revolutions must it take it cover 80π mm
1 n = 6  
2 n = 4  
3 n = 3  
4 n = 2  

Ans.

(2)

Outer circumference of Brooch B:

 =2π×10 mm=20π mmSuppose to cover 80π mm brooch B takes ncomplete revolutions. Then,20π×n=80π⇒n=4