Exams › JEE Main › Maths
A bag has 4 red balls and 4 blue balls. If 4 balls are drawn successively without replacement, what is the probability that the colours come out in alternating order?
- 35/6
- 2/35
- 3/35
- 6/35
Correct answer: 6/35
Solution
Alternating draws are RBRB or BRBR. P(RBRB) = (4/8)(4/7)(3/6)(3/5) = 144/1680, and P(BRBR) is the same. Total = 288/1680 = 6/35.
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 →