CA Foundation · Quantitative Aptitude · Statistical Description of Data
The marks of 40 students are grouped into equal-width classes. The lowest mark is 12 and the highest is 87. If the class width is taken as 10 and the first class starts at 10 (exclusive method), how many classes are needed to cover all the data?
Eight classes are needed. Starting at 10 with width 10, the classes run 10–20 up to 80–90, and the highest mark 87 falls in the eighth class 80–90. Using the range divided by width gives 7.5, which must be covered by 8 classes.
- A7
- B8Correct
- C9
- D10
Explanation
Classes starting at 10 are 10–20, 20–30, 30–40, 40–50, 50–60, 60–70, 70–80, 80–90. The highest mark 87 lies in 80–90, which is the 8th class. Computing (87-12)/10 = 7.5 and rounding down to 7 misses the last class needed.
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