The following table gives the number of children of 150 families in a village

Let the assume mean be $A=3$.

We know that mean, $\bar{X}=A+\frac{1}{N} \sum_{i=1}^{n} f_{i} d_{i}$

Now, we have $N=\sum f_{i}=150, \sum f_{i} d_{i}=-98$ and $A=3$

Putting the values above in formula, we get

$\bar{X}=A+\frac{1}{N} \sum_{i=1}^{n} f_{i} d_{i}$

$=3+\frac{1}{150} \times(-98)$

$=3-0.653$

$=2.347$

$\approx 2.35$ ( approximate)

Hence, the average number of children per family is 2.35.