Hitunglah keliling dan luas lingkaran berikut. a. d=35 cm

a. Keliling = 110 cm, Luas = 962.5 cm^2. b. Keliling ≈ 235.71 cm, Luas ≈ 4419.64 cm^2.

Pembahasan

Untuk menghitung keliling lingkaran, kita gunakan rumus K = πd, dan untuk luas lingkaran, kita gunakan rumus L = π(d/2)^2 atau L = (1/4)πd^2.

a. Jika diameter (d) = 35 cm:
Keliling (K) = πd = (22/7) * 35 cm = 22 * 5 cm = 110 cm.
Luas (L) = (1/4)πd^2 = (1/4) * (22/7) * (35 cm)^2 = (1/4) * (22/7) * 1225 cm^2 = (1/4) * 22 * 175 cm^2 = (1/2) * 11 * 175 cm^2 = 11 * 87.5 cm^2 = 962.5 cm^2.

b. Jika diameter (d) = 75 cm:
Keliling (K) = πd = (22/7) * 75 cm = 1650/7 cm ≈ 235.71 cm.
Luas (L) = (1/4)πd^2 = (1/4) * (22/7) * (75 cm)^2 = (1/4) * (22/7) * 5625 cm^2 = (1/4) * 22 * (5625/7) cm^2 = (11/2) * (5625/7) cm^2 = (11 * 5625) / 14 cm^2 = 61875 / 14 cm^2 ≈ 4419.64 cm^2.