The perimeter of a semi circular protractor is 32.4 cm. Calculate :
(i) the radius of protractor in cm, (ii) the arc of protractor in `cm^(2)`

Explanation

(i) Let the radius of protractor be r cm.
Perimeter of semicircle protractor `= (pi r + 2r) cm`
`:. R (pi + 2) = 32.4`
`rArr r ((22)/(7) + 2) = 32.4`
`rArr r xx (36)/(7) = 32.4 " " rArr r = (32.4 xx 7)/(36) rArr r = 6.3 cm`
Hence, radius of protractor = 6.3 cm
(ii) Area of semi circular protractor `= (1)/(2) pi r^(2)`
`= (1)/(2) xx (22)/(7) xx 6.3 xx 6.3 = 62.37 cm^(2)`
Hence, area of protractor `= 62.37 cm^(2)`