Question

The perimeter of a semi circular protractor is 32.4 cm find the radius of the protractor in cm and the area of the protractor is cm²

Answer 1

✯Given✯

➙ Perimeter of the semi-circular protractor = 32.4cm

✮To find✮

➙ Radius of the semi-circular protractor

➙ Area of the semi-circular protractor

✮Solution✮

➙ Let the radius of the protractor be r cm

➙ Then it's perimeter = (πr + 2r) cm

➙ πr + 2r = 32.4

➙ (π + 2)r = 32.4

➙ (²²⁄₇ + 2)r = 32.4

➙ ³⁶⁄₇ + 7r = 32.4

➙ r = 32.4 × ⁷⁄₃₆

➙ r = 6.3cm

✲Radius of the semi-circular protractor is 6.3 cm✲

➙  Area of the protractor = ½ × πr²

➙  Area of the protractor = ½ × ²²⁄₇ × 6.3 × 6.3

➙  Area of the protractor = 62.37

✲Area of the semi-circular protractor is 62.37cm²✲

➦ Semi-circular protractor is Semi circle (Half of a circle)

➙ Know more :-

• Area of circle =  πr²
• Circumference of circle =  2πr or  πd

⇒ r is radius and d is diameter