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NDA 2 2025 Maths, question 117

Topic: Statistics

Q117

The frequency distribution of the marks obtained by students in a Science examination is given below :

Marks 5–15 15–25 25–35 35–45
Number of students 20 30 30 20

What is the arithmetic mean?

  1. (a) 2020
  2. (b) 2525Correct answer
  3. (c) 3030
  4. (d) 3535

Solution.

Answer: (b) 2525

  1. Use class midpoints 10,20,30,40.
  2. The weighted sum is 20×10+30×20+30×30+20×40=2500 for 100 students.
  3. The estimated grouped mean is 2500/100=25.
  4. Symmetry about 25 provides a second check.