CA Foundation · Quantitative Aptitude · Probability
A box contains 6 white and 4 black balls. Four balls are drawn at random without replacement. What is the probability that exactly two are white and two are black?
The probability is 3/7. Total selections are 10C4 = 210, and the favourable ones are 6C2 x 4C2 = 15 x 6 = 90. Dividing 90 by 210 gives 3/7.
- A3/7Correct
- B1/2
- C4/7
- D2/7
Explanation
Total ways = 10C4 = 210. Favourable = 6C2 x 4C2 = 15 x 6 = 90. Probability = 90/210 = 3/7. The option 2/7 would come from using 60 favourable cases, which 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
- Two fair dice are rolled. Given that the sum of the numbers is 8, what is the probability that both dice show the same number?
- A manufacturing plant in Delhi produces widgets with a defect rate of 2%. Three widgets are selected at random and inspected. What is the pr…
- Ravi estimates that a venture will give a profit of Rs 50,000 with probability 0.3, a profit of Rs 20,000 with probability 0.5, and a loss o…
- Two events A and B of a random experiment cannot occur together in any single trial. Which of the following describes A and B?
- A box holds 5 red and 4 white balls. Three balls are drawn at random one after another without replacement. What is the probability that exa…
- The number of orders X received by an Ahmedabad trader in a day has the distribution: X = 0, 1, 2, 3 with probabilities 0.1, 0.3, 0.4, 0.2 r…