What is the diameter of a circle of area 77cm2 [Take (pi = frac{22}{7})]
-
A.
(frac{sqrt{2}}{7}cm) -
B.
(3frac{1}{2}cm) -
C.
7cm -
D.
(7sqrt{2}cm)
Correct Answer: Option D
Explanation
(A=pi r^2 Rightarrow 77 = frac{22}{7} times frac{r^2}{1}Rightarrow r^2 = frac{77times 7}{22} Rightarrow r^2 = frac{49}{2}\
Rightarrow r = sqrt{frac{49}{2}}=frac{7}{sqrt{2}}. Since D = 2r ∴ D = 2 times frac{7}{sqrt{2}} = frac{14}{sqrt{2}} times frac{sqrt{2}}{sqrt{2}} = 7sqrt{2}cm)