NCERT Solutions for Class 10 Science Chapter 12
Important NCERT Questions
Areas Related To Circles Class,
NCERT Books for Session 2022-2023
CBSE Board and UP Board Others state Board
EXERCISE 12.2
Page No:230
Questions No:9
A brooch is made with silver wire in the form of a circle with diameter 35 mm. The wire is also used in
making 5 diameters which divide the circle into 10 equal sectors as shown in Find.
(i) the total length of the silver wire required.
(ii) the area of each sector of the brooch.
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Diameter = 35 mm
Therefore, radius = 35/2 mm
(i) Total length of wire
= 5 × Diameter + Circumference = 5 × 35 + 2πr
= 175 + 2 × 22/7 × 35/2
= 175 + 110 = 285 mm
(ii) There are total 10 sectors.
Therefore, the angle of each sector = 360°/10° = 36°
Area of each sector
= 36°/360° × πr²
= 1/10 × π(35/2)²
= 1/10 × 22/7 × 35/2 × 35/2
= 385/4 mm²