Solution:
Given: In a continuous series,
Average marks (\(\overline x\)) = 40
and sum of their marks (∑fm) = 1200.
To find: No of students (N)
By formula,
\(\overline x=\frac{\sum fm}N\)
Or, \(40=\frac{1200}N\)
Or, \(40\times N=1200\)
Or, N = 30
∴ The number of students (N) = 30 is the required answer