Passage:
The adjoining histogram shows the frequency distribution of the ages of 20 teachers in a school. Based on the histogram, choose the correct option for each question.
The class size is
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 10
The class size (class width) is the difference between the upper and lower limits of a class. In this histogram the classes are 20-30, 30-40, 40-50 and 50-60, so each class is \(30-20=10\) years wide: the class size is 10.
Why the other options are incorrect
Option (1) 10-20 — Incorrect. This is a class interval itself (one with no teachers), not its width.
Option (3) 7 — Incorrect. This is the highest frequency, the 7 teachers of the 40-50 class.
Option (4) 20-60 — Incorrect. This is the span of all the classes together, made of four classes of 10 years each.