\begin{question}
Consider the following table:

<<echo = FALSE, results = tex>>=
d <- data.frame(
  Name = c("Fritz", "Wilhelm",  "Dieter", "Detlef"),
  Length = c(187, 161, 163, 195),
  Weight = c(85, 66, 66, 98)
)
m <- mean(d$Length)
knitr::kable(d, align = c("l", "r", "r", "l"), format = "latex")
@

What is the average of the variable ``Length''?
\end{question}


\begin{solution}
The average ``Length'' is \Sexpr{m}:

$$\bar x = \frac{\Sexpr{paste(d$Length, collapse = " + ")}}{4} = \Sexpr{m}.$$
\end{solution}


\exname{Calculate mean from table}
\extype{num}
\exsolution{\Sexpr{m}}
\extol{0.01}