: The given data is not having continuous class intervals. So, we have to add and subtract 0.5 to upper class limit and lower class limit.
Median class = 144.5-153.5
l = 144.5, h = 9, f = 12 and F = 17
Median = l + \(\frac{\frac{N}{2}-F}{f}\times h\)
\(=144.5+(\frac{20-17}{12})\times h\)
\(=144.5+\frac{9}{4}\)
= 146.75
So, median length is 146.75 mm.