Re: Four concentric circles share the same center. The smallest circle has
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19 May 2021, 01:04
First, we figure out the area of the smallest circle. A1=πr2=π12=π.
Now, we find the area of the second smallest circle (n=2). A2=A1+(2(2)−1)π=π+3π=4π. This means that the radius of the second smallest circle is 2 (since the area is πr2).
The third smallest circle has area A3=A2+(2(3)−1)π=4π+5π=9π. This means that the radius of this circle is 3.
Finally, the fourth smallest circle (that is, the largest circle) has area A4=A3+(2(4)−1)π=9π+7π=16π. This means that the radius of this circle is 4.
The sum of all the areas is π+4π+9π+16π=30π.
The sum of all the circumferences is 2π times the sum of all the radii. The sum of all the radii is 1+2+3+4=10, so the circumferences sum up to 20π.
Thus, the sum of all the areas, divided by the sum of all the circumferences, is 30π20π=112.
Answer: B