tentukan luas lingkaran jika diketahui jari jarinya 21 cm

L = 22/7 × 21 × 21
= 66 × 21 = 1386
Maaf kalau salah

[tex]luas \: lingkaran = \pi \times {r}^{2} \\ = \frac{22}{7} \times 21 \times 21 \\ \\ = \frac{22}{1} \times 3 \times 21 \\ \\ = 1386 {cm}^{2} [/tex]