hitunglah keliling dan luas lingkaran jika diketahui r=21 d=40

Keliling A
K = 2 x π x r
K = 2 x 22/7 x 21
K = 2 x 22 x 3
K = 132 cm

Keliling B
K = π x d
K = 3,14 x 40
K = 125,6 cm

Luas A
L = π x r²
L = 22/7 x 21²
L = 22/7 x 441
L = 22 x 63
L = 1386 cm²

Luas B
L = π x (d:2)²
L = 3,14 x (40 : 2)²
L = 3,14 x 20²
L = 3,14 x 400
L = 1256 cm

r = 21 cm
d = 2r
= 2 × 21
= 42 cm

keliling = π × d
= 22/7 × 42
= 132 cm

luas = π × r²
= 22/7 × 21²
= 22/7 × 441
= 1.386 cm²