judul kegiatan: menentukan luas dan keliling lingkaran. hitunglah keliling dan luas lingkaran yang memiliki ukuran berikut! A.diameter= 21 cm B.diameter=30 cm C

[tex]a)k = 2 \times \pi \times r \\ 2 \times 3.14 \times 10.5 \\ 2 \times 32.97 \\ 65.94 \: cm \\ l = \pi \times r \times r \\ 3.14 \times 10.5 \times 10.5 \\ 346.185 \: {cm}^{2} \\ b) k = 2 \times \pi \times r \\ 2 \times 3.14 \times 15 \\ 2 \times 47.1 \\ 94.2 \: cm \\ l = \pi \times r \times r \\ 3.14 \times 15 \times 15 \\ 706.5 \: {cm}^{2} \\ c)k = 2 \times \pi \times r \\ 2 \times \frac{22}{7} \times 14 \\ 2 \times 44 \\ 88 \: cm \\ l = \pi \times r \times r \\ \frac{22}{7} \times 14 \times 14 \\ \frac{22}{7} \times 196 \\ 616 \: {cm}^{2} \\ k = 2 \times \pi \times r \\ 2 \times 3.14 \times 20 \\ 2 \times 62.8 \\ 125.6 \: cm \\ l = \pi \times r \times r \\ 3.14 \times 20 \times 20 \\ 1256 \: {cm}^{2} [/tex]

A.) K = 2 . phi . r
= 2 . 3,14 . 10,5
= 65,94 cm
L = phi . r²
= 3,14 . 10,5 . 10,5
= 336,185 cm²
C.) K = 2 . phi . r
= 2 . 22/7 . 14
= 88 cm
L = phi . r²
= 22/7 . 14 . 14
= 716 cm²