\begin{equation*}
(n-1)s + 1 = 5 \cdot 0.42 + 1 = 2.1 + 1 = 3.1
\end{equation*}
and so in this case m = 3 and r = 0.1. Thus, the percentile will lie between \(y_3 = 54\) and \(y_4 = 64\) and much closer to 54 than 64. Numerically
\begin{equation*}
P^{0.42} = 0.9 \cdot 54 + 0.1 \cdot 64 = 55.
\end{equation*}