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1.r=21 cm
luas=Π×r×r
=22/7×21×21
=1.386 cm
2.r=30cm
luas=Π×r×r
=3,14×30×30
=282.600cm
3.r=49cm
=Π×r×r
=22/7×49×49
=7.546cm
4.d=12cm
=1/4×3,14×12×12
=1/4×45.216
=11.304cm
5.d=35cm
=1/4×22/7×35×35
=1/4×3.850
=962,5cm
6.d=40
=1/4×3,14×40×40
=1/4×5.024
=1.256cm