Question

Area of protactor is 18.25 cm^2 find its perimeter

Answer 1

We know that a protactor is in the form of a semi circle therefore,

Area of protactor = Area of semi circle
18.25 cm ^ 2 = 1/2 * π * r ^ 2
π r ^ 2 = 18.5
r ^ 2 = 18.5 / π
r ^ 2 = ( 18.5 / 22 ) * 7
r ^ 2 = 129.5 / 22
r = 2.4262 cm ( approximately )
r = 2.43 cm ( approximately )

Perimeter of semi circle = π * r
P = 22/7 * 2.43
P = 22 * 0.35
P = 7.7 cm

Hence,

Perimeter of protactor = 7.7 cm

Answer 2

Area of protractor = 18.52




1/2 × πR² = 18.52





1/2 × 22/7 × R² = 18 . 52






22 / 14 × R² = 18.52



R² = ( 18.52 × 14 / 22 )


R² = ( 259.28 / 22 )


R² = 11.78


R = √11.78 = 3.43 cm.




Therefore,


Perimeter of protector = ( πR + 2R )





Perimeter of protector = ( 22/7 × 3.43 + 2 × 3.43 ) = ( 75.46 / 7 + 6.86 ) = ( 1.06 + 6.86 ) = 7.92 cm.