**Q) **The length of 40 leaves of a plant are measured correct to nearest millimetre, and the data obtained is represented in the following table:

Find the mean length of the leaves.

**Ans: **

Let’s re-arrange the data with midpoint of each class, frequency, and multiply midpoint with frequency:

We know that, mean value of grouped data is given by:

Mean value =

From above table with rearranged data, we get the following values:

= 5879

_{ }= 40

Therefore, Mean value = = 146.975 mm

**Hence, the mean length of the leaves is 146.975 mm.**