JAMB 1994 · UME · Q49

The table shows the number of pupils in each age group in a class. What is the probability that a pupil chosen at random is at least 11 years old?

Age in years 10 11 12
Number of pupils 6 27 7
Worked solution (try it first)
  1. There are 6+27+7=406 + 27 + 7 = 40 pupils.
  2. At least 11 means 11 or 12: 27+7=3427 + 7 = 34 pupils.
  3. So the probability is 3440=1720\frac{34}{40} = \frac{17}{20}, option B.

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