Hitunglah keliling dan luas lingkaran jika diketahui : 1) panjang jari jarinya 28 cm, 2) berdiameter 30 cm

a)keliling
= 2 ×phi × r
= 2 × 22/7 × 14
= 2 × 44
= 88 cm

luas
= phi × r^2
=22/7 × 14^2
= 22/7 × 196
= 22 × 28
= 616 cm^2 b)keliling = 2 ×phi × r = 2 × 3,14 × 15 = 94,2 cm luas =phi × r^2 = 3,14 × 15 ×15 =3,14 ×225 =706,5 cm^2