Sebuah lingkaran luasnya 154 cm2,maka kelilingnya adalah...

L = πr^2
154 = 22/7 × r^2
r^2 = 154 : 22/7
r^2 = 154 × 7/22 = 49
r = √49 = 7
keliling = 2πr = 2 × 22/7 × 7 = 44/7 × 7 = 44 cm

Mapel Matematika
Bab Lingkaran

Luas = πr^2
154 = (22/7)r^2
1078 = 22r^2
r^2 = 49
r = 7 cm

Keliling = 2πr
Keliling = 2 x (22/7) x 7
Keliling = 44 cm