diff -r 8999d0a3fc9d -r 5dc6c3673f9d day1/session4.tex
--- a/day1/session4.tex	Sun Jan 10 23:09:00 2010 +0530
+++ b/day1/session4.tex	Tue Jan 12 19:03:34 2010 +0530
@@ -646,7 +646,7 @@
 \begin{lstlisting}
   In []: x = array([[1,2,3,4]])
 \end{lstlisting}
-How to \lstinline+x+ to \lstinline+array([[1,2,0,4]])+?
+How to change \lstinline+x+ to \lstinline+array([[1,2,0,4]])+?
 \end{frame}
 
 \begin{frame}[fragile]
@@ -665,6 +665,17 @@
 \begin{frame}[fragile]
 \frametitle{\incqno }
 \begin{lstlisting}
+  In []: x = array([[9,18,27],
+                    [30,60,90],
+                    [14,7,1]])
+\end{lstlisting}
+What is the output of \lstinline+x[::3,::3]+
+\end{frame}
+
+
+\begin{frame}[fragile]
+\frametitle{\incqno }
+\begin{lstlisting}
 In []: a = array([[1, 2],
                   [3, 4]])
 \end{lstlisting}