1. Hitunglah keliling lingkaran jika : a. r = 7cm b. r = 10cm c. d = 21cm d. d = 20cm

1.a.
r = 7 cm
D = 14 cm
22/7 x 14 cm = 44cm2

1.b.
r = 10 cm
D = 20 cm
3,14 x 20 cm = 62,8 cm2

1.c.
D = 21 cm
22/7 x 21 cm = 66 cm2

1.d.
D = 20 cm
3,14 x 20 cm = 62,8 cm2

a. K = 2[tex] \pi [/tex]r
       = 2.22/7.7
       = 44 cm

b. K = 2[tex] \pi [/tex]r
       = 2.3,14.10
       = 62,8cm

c. K = [tex] \pi [/tex]d
       = 22/7.21
       = 66cm

d. K = [tex] \pi [/tex]d
       = 3,14.20
       = 62,8cm