Question
A box contains 4 red, 5 blue, and 3 green balls. Two
balls are drawn at random without replacement. What is the probability that the two balls drawn are of different colours?Solution
ATQ, Total balls = 4 + 5 + 3 = 12. Total ways to draw 2 balls = C(12,2) = 66. Number of ways to draw 2 of the same colour: Red: C(4,2) = 6 Blue: C(5,2) = 10 Green: C(3,2) = 3 Total same-colour ways = 6 + 10 + 3 = 19. Thus different-colour ways = 66 − 19 = 47. Required probability = 47 / 66.
Lucas, Maya, and Riley can build a wall in 5, 10, and 15 days respectively. If they start the job together and Lucas leaves 3 days before the job is don...
(x + 7) workers finish 60% of a job in 9 days working 4 hours/day. The remaining work is done by (x + 3) workers in 12 days working 3 hours/day. Find x.
A can complete a job in 12 days, B in 18 days. They work together for 6 days, then A leaves. How many more days will B take to finish the remaining work?
A alone can complete a work in 18 days, and B alone can complete the same work in 24 days. They start working together, but A leaves after 4 days. In ho...
A tank is filled by three pipes with uniform flow. The first two pipes operating simultaneously fill the tank in the same time during which the tank is ...
‘X’ is 25% more efficient than ‘Y’, and ‘Z’ is 25% less efficient than ‘Y’. Together, they can complete a job in 40 days. If X and Y wor...
5 men and 5 women can do some work in 2 days. If each man is 25% more efficient than a woman, then find the time taken by 9 men to finish the same work...
A 6 km long boundary wall is to be built by 32 workers. After 15 days, only 3/4 of the wall is completed. Then 8 more workers join them. In how many da...
- Working 6 hours a day, Rahul can complete a work in 25 days. How many hours a day should he work to complete the same work in 15 days?
'B' and 'N' can collectively finish a task in 88 days, and 'N' and 'S' together can complete the same work in 66 days. If 'B' and 'S' work together, the...
