In a frequency distribution if mode is 40 and median is 20 then mean will be?

Concept: Karl Pearson's Formula can be used to express the relationship between mean, median, and mode:

$\Rightarrow Mode=3Median-2Mean$

Given: Mode = 40 and Median = 20

$\begin{array}{l}\Rightarrow Mode=3Median-2Mean\\ \Rightarrow 40=3\left(20\right)-2Mean\\ \Rightarrow 40=60-2Mean\\ \Rightarrow 2Mean=60-40=20\\ \Rightarrow Mean=\frac{20}{2}=10\\ \therefore Mean=10\end{array}$

Hence, mean is 10.