Moderate -0.8 This is a straightforward logarithm manipulation requiring students to take logs of both sides and rearrange to isolate y/x. It's a standard textbook exercise testing basic log laws with no problem-solving insight needed, making it easier than average but not trivial since it requires correct algebraic manipulation.
1 Given that $13 ^ { x } = ( 2.8 ) ^ { y }$, use logarithms to show that $y = k x$ and find the value of $k$ correct to 3 significant figures.
\hfill \mbox{\textit{CAIE P2 2010 Q1 [3]}}