If (y alpha frac{1}{x^2}) and (y = 1frac{1}{4}) when x = 4, find the value of y when (x = frac{1}{2})
-
A.
(2frac{1}{2}) -
B.
5 -
C.
10 -
D.
80
Correct Answer: Option D
Explanation
(y propto frac{1}{x^2} Rightarrow y = frac{k}{x^2} Rightarrow k = yx^2\
k = 1frac{1}{4} times 4^2 Rightarrow k=frac{5}{4}times frac{16}{1}=20\
∴y = 20 div left(frac{1}{2}right)^2=20times frac{4}{1}=80)