WAEC - Mathematics (2005 - No. 43)

If y  \(\alpha\)  x\(^2\) and y = 1\(\frac{1}{4}\) when x = 4, find the value of y when x = \(\frac{1}{2}\)
\(2\frac{1}{2}\)
5
10
80

Explanation

y \(\propto x^2\), y = 1\(\frac{1}{4}\), x = 4

y = \(\frac{\text{k}}{x^2}\) 

k = y x\(^2\) = \(\frac{5}{4}\) x 4\(^2\) = 20

y = \(\frac{20}{x^2}\) =  \(\frac{20}{x^2}\) = \(\frac{20}{(\frac{1}{2})^2}\)

= \(\frac{20}{\frac{1}{4}}\) = 20 x 4 = 80

 

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