Circle - simple

Calculate the area of a circle in dm2, if its circumference is 31.4 cm.

Result

S =  0.78 dm2

Solution:

31.4=2πr r=0.5 dm S=πr2=0.78 dm231.4 = 2\pi r \ \\ r = 0.5 \ dm \ \\ S = \pi r^2 = 0.78 \ \text{dm}^2

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