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?
Attached Figure / Diagram
A
27/40
B
17/20
C
3/30
D
33/40
Verified Correct Answer: B.
Step-by-Step Mathematical Solution
P(At least 11 yrs) = P(11yrs) + P(12yrs)
= \(\frac{27}{40}\) + \(\frac{7}{40}\)
= \(\frac{34}{40}\)
= \(\frac{17}{20}\)
Source: Myschool Past Questions Archive (Record #9152)