(begin{array}{c|c} text{Age in years} & 10 & 11 & 12 \ hline text{Number of pupils} & 6 & 27 & 7end{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?
-
A.
(frac{27}{40}) -
B.
(frac{17}{20}) -
C.
(frac{33}{40}) -
D.
(frac{3}{20})
Correct Answer: Option B
Explanation
Total number of pupils = 7 + 27 + 6 = 40
n(at least 11 years old) = 27 + 7 = 34.
P(picking a pupil who is at least 11 years old) = (frac{34}{40} = frac{17}{20}).