waecmaths question:
Find the mean deviation of 20, 30, 25, 40 35, 50, 45, 40, 20 and 45
Option A:
8
Option B:
9
Option C:
10
Option D:
12
waecmaths solution:
$\begin{align} & Mean=\bar{x}=\frac{20+30+25+40+35+50+45+40+20+45}{10} \\ & Mean=\bar{x}=\frac{350}{10}=35 \\ & \text{Mean deviation}=\frac{\left| 20-35 \right|+\left| 30-35 \right|+\left| 25-35 \right|+\left| 35-35 \right|+\left| 50-35 \right|+\left| 45-35 \right|+\left| 40-35 \right|+\left| 20-35 \right|+\left| 45-35 \right|}{10} \\ & \text{Mean deviation}=\frac{85}{10}=8.5 \\\end{align}$
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