CA Foundation · Quantitative Aptitude · Probability
In a class of Chartered Accountancy aspirants, the probability that a randomly chosen student has opted for coaching in Accounting is 0.55, the probability that the student has opted for coaching in Law is 0.45, and the probability that the student has opted for at least one of the two is 0.80. What is the probability that the student has opted for both?
The probability of opting for both is 0.20. Using the addition theorem, P(A or B) equals P(A) plus P(B) minus P(A and B), so P(A and B) is 0.55 plus 0.45 minus 0.80, which gives 0.20.
- A0.10
- B0.20Correct
- C0.25
- D0.35
Explanation
By the addition theorem, P(A and B) = P(A) + P(B) - P(A or B) = 0.55 + 0.45 - 0.80 = 0.20. The value 0.10 results from subtracting 0.90 mistakenly, and 0.25 is not derivable from the data. Option 0.35 is wrongly P(A or B) - P(A) ... incorrectly taken, so it is wrong.
Did you get it right without looking?
One question tells you little. A timed set on Probability shows your real accuracy, how long you take and where you lose marks.
More Probability questions
- A single fair die is thrown once. Which of the following pairs of events is mutually exclusive?
- A bank in Chennai finds that 20% of its loan customers are defaulters. Past records show that 80% of defaulters had a poor credit score, whi…
- A, B and C are three events with P(A) = 0.5, P(B) = 0.4, P(C) = 0.3, P(A∩B) = 0.2, P(B∩C) = 0.1, P(A∩C) = 0.15 and P(A∩B∩C) = 0.05. What is …
- A box contains 20 tickets numbered 1 to 20. One ticket is drawn at random. What is the probability that the number is a multiple of 3 or a m…
- A fair coin is tossed three times. What is the probability of getting at least two heads?
- For two events A and B, P(A) = 0.6, P(B) = 0.5 and P(A ∩ B) = 0.3. What is P(B | A)?