Inverse-root difference and scale change

The quantity \(y\) varies inversely with \(\sqrt{x}\). The difference between its values at \(x=9\) and \(x=16\) is \(5\). Find \(x\) when \(y=10\).

The quantity \(v\) is inversely proportional to \(x^2\). If \(x\) is multiplied by \(4\), find the percentage change in \(v\).