Question

from a square cardboard of side 21cm ,a circle of maximum area is cut out . find the area of the card board left

Answer 1

Diameter of circle =Side of square
Diameter of circle = 21 cm
Radius of circle = 21 /2 cm

Area of circle = pi *r^2
= 22 * 21 * 21 /7 * 2* 2
= 22 * 21 * 3 / 4
= 462 * 3 /4
= 1386/4
= 346.5 cm^2

Area of cardboard left = Area of square - Area of circle
Area of cardboard left = 21*21 - 346.5
= 441 - 346.5
= 94.5 cm^2

Answer 2

square area=S×S=21×21=441cm
perimeter of square=21×4=84cm

C=84cm
C=2πr
84=2×22/7×r
84×7/44=r
13.36=r


A=πr²
=22/7×13.36²
=560.96cm²




cardboard left=(560.96-441)cm²
=119.96cm²