hitunglah keliling lingkaran jika diketahui a. r = 20 cm b. r = 4,2 cm c. d = 35 cm d. d = 40 cm tolong di jawab cepet yh kak soal nya butuh

Keliling lingkaran

A. r = 20 cm
[tex]k = 2 \: \pi \: r \\ \: \: \: = 2 \times 3.14 \times 20 \\ \: \: \: = 125.6 \: cm ^{2} [/tex]
B. r = 4,2 cm
[tex]k = 2 \times 3.14 \times 4.2 \\ \: \: \: = 26.376 \: {cm}^{2} [/tex]
C. d = 35 cm, r = 17,5 cm
[tex]k = 2 \times 3.14 \times 17.5 \\ \: \: \: = 109.9 {cm}^{2} [/tex]

d. d=40 cm, r = 20 cm
[tex]k = 2 \times 3.14 \times 20 \\ \: \: \: = 125.6 {cm}^{2} [/tex]