Exams › JEE Main › Maths

A random variable X has the distribution: X = 1,2,3,4,5,6,7,8 with probabilities 0.15, 0.23, 0.12, 0.10, 0.20, 0.08, 0.07, 0.05 respectively. For events E = {X is prime} and F = {X < 4}, find P(E union F).

1. 0.35
2. 0.77
3. 0.87
4. 0.50

Correct answer: 0.77

Solution

Combining primes {2,3,5,7} with {1,2,3} gives the outcome set {1,2,3,5,7}; summing their probabilities gives 0.77.

Related JEE Main Maths questions

• A random variable can assume the values 0, 1, 2,..., n, and its corresponding frequencies are proportional to the coefficients nC0, nC1, nC2,..., nCn. What is the variance of this distribution?
• From the integers 1, 2, 3,..., 2004, two distinct numbers x and y are selected at random without replacement. What is the probability that x³ + y³ is divisible by 3?
• One card is selected at random from a standard deck of 52 cards. A player wagers that the card will be a spade or an ace. What are the odds against the player winning the wager?
• When n objects are assigned randomly to n people, what is the probability that at least one person receives no object?
• For two arbitrary events M and N, what is the probability that one and only one of them happens?
• A four-digit number is made using the digits 1, 2, 3, and 4 without repeating any digit. What is the probability that the resulting number is odd?

⚔️ Practice JEE Main Maths free + battle 1v1 →