Question
========
Consider the following table:

```{r, echo = FALSE, results = "asis"}
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 = "markdown")
```

What is the average of the variable "Length"?


Solution
========
The average "Length" is `r m`:

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


Meta-information
================
exname: Calculate mean from table
extype: num
exsolution: `r m`
extol: 0.01
