berapa luas dan keliling lingkaran jika,d=21

L = (1/4)πd²
= (1/4) x 22/7 x 21 cm x 21 cm
= 346,5 cm³

K = πd
= 22/7 x 21 cm
= 66 cm

diket : d = 21
r = 21/2
= 7

luas = phi × r2
= 22/7 × 7 × 7
= 154 cm
keliling = 2 × phi × r
= 2 ×22/7×7
= 2× 154
= 308 cm