Find the mean of each of the following frequency distributions :

Let the assumed mean be A = 100 and h = 20.

We know that mean $\bar{X}=A+h\left(\frac{1}{N} \sum f_{i} u_{i}\right)$

Now we have $N=\sum f_{i}=100, \sum f_{i} u_{i}=61, h=20$ and $A=100$

Putting the values in the above formula, we get

$\bar{X}=A+h\left(\frac{1}{N} \sum f_{i} u_{i}\right)$

$=100+20\left(\frac{1}{100} \times(61)\right)$

$=100+\frac{1220}{100}$

$=100+12.20$

$=112.20$

Hence, the mean is 112.20.