\(\begin{array}{c|c} \text{Age in years} & 10 & 11 & 12 \\ \hline \text{Number of pupils} & 6 & 27 & 7\end{array}\)
The table above 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?
The correct answer is B. \(\frac{17}{20}\)
From the table, we can see that there are 6 pupils who are 10 years old, 27 pupils who are 11 years old, and 7 pupils who are 12 years old. So, the total number of pupils in the class is 6 + 27 + 7 = 40.
The probability that a pupil chosen at random is at least 11 years old is equal to the number of pupils who are at least 11 years old divided by the total number of pupils in the class. Since there are 27 pupils who are 11 years old and 7 pupils who are 12 years old, there are a total of 27 + 7 = 34 pupils who are at least 11 years old.
So, the probability that a pupil chosen at random is at least 11 years old is \(\frac{34}{40}\) = \(\frac{17}{20}\).
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