Percentage in Middle Range Classes

In a frequency distribution of marks of 100 students, 63 students were concentrated in three classes 40–50, 50–60 and 60–70. What percentage does this represent?

Correct Answer Explanation

63 students out of 100 = 63% concentrated in the middle range 40–70.

Breakdown:

• 40–50: 21 students
• 50–60: 23 students
• 60–70: 19 students
• Total = 21 + 23 + 19 = 63 students = 63%

Key Insight:

• The remaining 37% are in the classes 0–10, 10–20, 20–30, 30–40, 70–80, 80–90, and 90–100.
• These classes are sparsely populated — this is why unequal class intervals (smaller intervals in the 40–70 range) are used.