Question

a sector of a circle of radius 7 cm standing and angle of 270 degree at the centre of the circle is used to form a cone find the base radius of the cone and calculate the area of the base of the cone

Answer 1

360 - 270 = 90 degrees

so the circumference of the base = (3/4) (2 pi R) = (3/4) of the original circumference
so the radius of the cone base = (3/4) * original radius = (3/4)*7 = 5.25 cm
area of that base = pi r^2
= pi * 5.25^2