berapa luas lingkaran. jika kelilingnya 22 cm

k =2 × phi x r

22 = 2 × 22/7 × r

r = 22× 7 / 22× 2
= 154 / 44 = 3.5

L = phi x r x r
= 3,14 × 3,5 × 3,5 = 38,465 atau 38,5