consider the given data set
\begin{array} {|r|r|} \hline class & frequency \\ \hline 0-10 &4 \\ \hline 10-20 &10 \\ \hline 20-30 &10 \\ \hline 30-40 &10 \\ \hline 40-50 &6 \\ \hline 50-60 &4 \\ \hline \end{array}
I know the formula $$Mode=l+h(\frac{f_m-f_1}{2f_m-f_1-f_2})$$
but this table has three mode classes
how to proceed
my prooblem is what are the modes? how to use the formula to this problem? (since formula gives dividing by zero)
When modal class is repeated, Mode cannot be estimated directly using the formula you quoted. Instead use the following formula for such cases:
$$Z = 3M - 2\bar{X}$$
where $Z$ is the mode, $M$ is the Median and $\bar{X}$ is the Mean.