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1) r = 21 cm

a. Diameter
d = 2r
d = 2(21 cm)
d = 42 cm

b. Luas
L = πr²
L = 22/7 x 21 cm x 21 cm
L = 1386 cm²

c. Keliling
K = π x d
K = 22/7 x 42 cm
K = 132 cm

2) K = 88 cm dan π = 22/7

a. Jari-jari
K = 2πr
88 cm = 2 x 22/7 x r
88 cm = 44/7 x r
r = 88 cm x 7/44
r = 14 cm

b. Luas
L = πr²
L = 22/7 x 14 cm x 14 cm
L = 616 cm²