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If y alpha frac 1 x 2 and y 1 frac 1 4 when x 4... - WAEC Mathematics 2005 Question

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