2026 · Q99
Consider the following incomplete frequency distribution with a total frequency of 100 : Class – Frequency : 0–10 – 10; 10–20 – x; 20–30 – 20; 30–40 – y. If the mean of the frequency distribution is 25, then what are the missing frequencies?
Elementary MathematicsStatistics
- Ax = 15, y = 55
- Bx = 50, y = 20
- Cx = 20, y = 45
- Dx = 25, y = 45
Explanation
Total frequency 100 gives 10 + x + 20 + y = 100, i.e. x + y = 70. With class midpoints 5, 15, 25, 35, mean 25 gives (50 + 15x + 500 + 35y)/100 = 25, i.e. 3x + 7y = 390. Solving with x + y = 70: 3x + 7(70 − x) = 390 gives x = 25 and y = 45, option D.