If the mean deviations about the median of the numbers a, 2a, 3a,……..50a is 50, then |a| =

Median of a, 2a, 3a……50a is $\frac{25\mathrm{a}+26\mathrm{a}}{2}=\left(25.5\right)\mathrm{a}$

M.D (about median) = $=\frac{\sum _{\mathrm{i}=1}^{50} \mid {\mathrm{x}}_{\mathrm{i}}=\text{ median }\mid }{\mathrm{N}}\Rightarrow 50=\frac{1}{50}\left[2\right|\mathrm{a}\left|\right(0.5+1.5+2.5+\dots \mathrm{.524.5}\left)\right]$

$\Rightarrow 2500=2\left|\mathrm{a}\right|\frac{25}{2}\left(25\right)\Rightarrow \left|\mathrm{a}\right|=4$