What is the area between two concentric circles of diameters 26cm and 20cm?
-
A.
100(pi) -
B.
169(pi) -
C.
69(pi) -
D.
9(pi) -
E.
269(pi)
Correct Answer: Option C
Explanation
Area of circle 1 with diameter 26cm:
(pi r^{2} = pi times (frac{26}{2})^{2} )
= (169 pi cm^{2})
Area of circle 2 with diameter 20 cm:
(pi R^{2} = pi times (frac{20}{2})^{2})
= (100 pi cm^{2})
Area between the two circles = ((169 – 100) pi cm^{2})
= (69 pi cm^{2})