Home › JEE Main › mathematics › Statistics and Probability › Three fair coins are tossed. Let E = "at least t…
Three fair coins are tossed. Let E = "at least two heads" and F = "first coin shows tail". Then P(E|F) is
A{'text': '1/4', 'label': 'A'}
B{'text': '1/8', 'label': 'B'}
C{'text': '1/2', 'label': 'C'}
D{'text': '3/8', 'label': 'D'}
Answer & Solution
Correct answer: A. {'text': '1/4', 'label': 'A'}
1. Sample space of 3 coins has 8 equally likely outcomes.
2. E = {HHH, HHT, HTH, THH}, F = {THH, THT, TTH, TTT}.
3. E ∩ F = {THH}, so P(E ∩ F) = 1/8; P(F) = 4/8 = 1/2.
4. P(E|F) = P(E ∩ F) / P(F) = (1/8) / (1/2) = 1/4.
_Source: NCERT Class 12 Mathematics, Ch 13 "Probability", §13.2_
Related questions
For a random variable X, the variance Var(X) equalsIf P(A) = 0.4, P(B|A) = 0.5, then P(A ∩ B) equalsTwo dice are rolled. Let E = "sum is 8" and F = "at least one die shows 4". Then P(E|F) eqE and F are independent events with P(E) = 0.3 and P(F) = 0.5. Then P(E ∪ F) equalsA card is drawn at random from a well-shuffled deck of 52. E = "card is a face card" (KingFor a Binomial distribution B(n, p), the probability of exactly r successes isThe variance of the number of heads in 3 fair-coin tosses isA random variable X counts the number of heads in 3 tosses of a fair coin. The mean E(X) i