Jambmaths question:
The mean of the numbers 3, 6, 4,x, and 7 is 5. Find the standard deviation.
Option A:
$\sqrt{2}$
Option B:
$\sqrt{3}$
Option C:
2
Option D:
3
Jamb Maths Solution:
$\begin{align} & mean=\overline{x}=\frac{3+6+4+x+7}{5} \\ & 5=\frac{20+x}{5} \\ & x=25-20=5 \\ & variance=\frac{{{(3-5)}^{2}}+{{(4-5)}^{2}}+{{(5-5)}^{2}}+{{(6-5)}^{2}}+{{(7-5)}^{2}}}{5} \\ & variance=\frac{4+1+0+1+4}{5}=\frac{10}{5}=2 \\ & standard variance=\sqrt{variance}=\sqrt{2} \\\end{align}$
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