Find the mean deviation about the mean for the data

$N=\sum_{i=1}^{5} f_{i}=80, \sum_{i=1}^{5} f_{i} x_{i}=4000$

$\therefore \overline{\mathrm{x}}=\frac{1}{\mathrm{~N}} \sum_{\mathrm{i}=1}^{5} \mathrm{f}_{\mathrm{i}} \mathrm{x}_{\mathrm{i}}=\frac{1}{80} \times 4000=50$

$\operatorname{MD}(\bar{x}) \frac{1}{N} \sum_{i=1}^{5} f_{i}\left|x_{i}-\bar{x}\right|=\frac{1}{80} \times 1280=16$