CA Foundation · Quantitative Aptitude · Probability
In a class of 40 students at a Jaipur coaching centre, 24 study Accounting, 16 study Economics and 8 study both. A student is chosen at random and is found to study Accounting. What is the probability that the student also studies Economics?
The probability is 1/3. Once we know the student studies Accounting, the sample space shrinks to the 24 Accounting students, of whom 8 also study Economics, so the conditional probability is 8/24 = 1/3.
- A1/5
- B1/3Correct
- C1/2
- D2/3
Explanation
P(Acc) = 24/40 and P(Acc and Eco) = 8/40. Conditional probability P(Eco | Acc) = 8/24 = 1/3. The option 1/5 is P(both) = 8/40, which wrongly divides by the whole class instead of the Accounting students.
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