Question
A box contains 21 ribbons out of which [A] ribbons are
white, and rest is green in colour. The probability of drawing a white ribbon and a green ribbon together is 18/35. Now, [B] green ribbons are added in the box such that the probability of drawing a green ribbon from the box is 1/2. Now, [C] yellow ribbons are added to the box such that the probability of drawing a yellow ribbon from the box is 1/5. Find the value of C-B?Solution
Let number of white ribbons in the box is ‘x’. Number of green ribbons in the box = (21 – x) According to question, [x × (21 – x)]/ 21C2 = 18/35 x (21 – x)/210 = 18/35 x (21 – x) = 18 × 6 x2 – 21x + 108 = 0 x = 12 or x = 9 So, the box contains either 12 white ribbons and 9 green ribbons or 9 white ribbons and 12 green ribbons. Now, if ‘B’ green ribbons are added and probability of drawing a green ribbon from the box becomes 1/2, it means number of green ribbons was less than number of white ribbons in the box initially. So, the numbers of white and green ribbons in the box initially were 12 and 9 respectively. Therefore, [A] = 12 and [B] = 3. Let number of yellow ribbons added in the box be ‘z’. So, [z/ (21 + 3 + z)] = 1/5 5z = z + 24 4z = 24 z = 6 So, [C] = 6 Required difference = 6-3 = 3
The average of the first and second numbers is 20, while the average of the second and third numbers is 25. If the sum of the first and third numbers is...
Average weight of all the people in a group is 58 kg. When two people of weight 65 kg and 81 kg left the group, average weight reduces by 1.2 kg. Find t...
Out of three numbers the average of the first and the second number is 37 more than the average of the second and the third number. What is the differen...
The average age of each of the 20 employees in an IT company is 20 years. When you include the age of the Team leader, the company's average age becomes...
The average of 17 numbers is 80. The first seven numbers have an average of 100, and the last five numbers have an average of 72. The tenth number exce...
- If the average of 30 values is 58 and each of these values is multiplied by 7, what will be the new average?
Five friends each contributed Rs. 70. If the sixth friend gives Rs. 50 more than the average contribution of all six, how much did the sixth friend cont...
The average age of husband, wife and their child 4 years ago was 26 years and that of wife and the child 5 years ago was 25 years. The present age of th...
- The average age of (x + 1) students of a class is 20 years. If the 50 years old class teacher is also included then average age of the class gets increased...
The number of students in class 'A' is 140, and the ratio of girls to boys is 9:5. If the average number of boys in classes A and B is 160, and the aver...
