Ans: (a) $28$ (b) Range $=5$, inter-quartile range $=2$, standard deviation $=1.43$
-
$\begin{array}{rcl}
\dfrac{12+k+16}{12+k+16+9+11+4} & = & \dfrac{7}{10} \\
280+10k & = & 364+7k \\
3k & = & 84 \\
k & = & 28
\end{array}$ -
$\begin{array}{rcl}
\text{Range} & = & 28 – 23 \\
& = & 5
\end{array}$$\begin{array}{rcl}
\text{Inter-quartile range} & = & 26 – 24 \\
& = & 2
\end{array}$$\begin{array}{rcl}
\text{Standard deviation} & = & 1.43 \\
& = & 2
\end{array}$
