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Lingkaran A

d = 200 cm

r = 100 cm

L = πr² = 3,14 × 100² = 3,14 × 100 = 314 cm²

Lingkaran B

d = r × 2 = 30 × 2 = 60 cm

r = 30 cm

L = πr² = 3,14 × 30² = 3,14 × 900 = 2.826 cm²

Lingkaran C

d = 42 cm

r = d/2 = 42/2 = 21 cm

L = πr² = 22/7 × 21² = 22/7 × 441 = 1.386 cm²

Lingkaran D

d = r × 2 = 28 × 2 = 56 cm

r = 28 cm

L = πr² = 22/7 × 28² = 22/7 × 784 = 2.464 cm²

Lingkaran E

L = πr²

154 = 22/7 × r²

r² = 154 ÷ 22/7

r² = 154 × 7/22

r² = √49

r = 7 cm

d = r × 2 = 7 × 2 = 14 cm

Lingkaran F

L = πr²

314 = 3,14 × r²

r² = 314/3,14

r² = √100

r = 10 cm

d = r × 2 = 10 × 2 = 20 cm