A bag contains 15 balls of which x are blue ball and the remaining are...
Answer:
No. of balls = 15
No. of blue balls = x
No. of red balls = 15 - x
So , P (red ball) = 15 - x / 15
Now
No. of red balls increased by 5
P (red ball) = 15 - x + 5 / 15 + 5
= 20 - x / 20
According to Question,
20 - x / 20 = 2 (15 - x / 15)
> 20 - x / 40 = 15 - x / 15
> 60 - 3x = 120 - 8x
> 5x = 60
> x = 12
Hence,
No. of red balls = 15 - 12 = 3
No. of blue balls = 12
i. P (red ball) = 3 / 15 = 1 / 5
ii. P (blue ball) = 12 / 15 = 4 / 5
iii. P (blue ball if actually 5 red balls added) = 12 / 20 = 3 / 5
This question is part of UPSC exam. View all Class 10 courses
A bag contains 15 balls of which x are blue ball and the remaining are...
Given information:
- The bag contains 15 balls.
- Let x be the number of blue balls.
- The remaining balls are red.
- When the number of red balls is increased by 5, the probability of drawing red balls doubles.
To find:
(1) P(red balls)
(2) P(blue ball)
(3) P(blue ball if 5 extra red balls are added)
Solution:
1. P(red balls):
Let's assume the number of red balls initially is r.
Since the total number of balls in the bag is 15, we can write the equation:
x + r = 15
The probability of drawing a red ball from the bag initially is given by:
P(red balls initially) = r/15
When the number of red balls is increased by 5, the new number of red balls becomes r + 5.
According to the given condition, the probability of drawing a red ball doubles. So, we can write the equation:
2 * P(red balls initially) = P(red balls after increasing by 5)
Substituting the values, we get:
2 * (r/15) = (r + 5)/15
Simplifying the equation:
2r = r + 5
r = 5
Therefore, there are initially 5 red balls in the bag.
So, the probability of drawing red balls is:
P(red balls) = 5/15 = 1/3
2. P(blue ball):
We know that the total number of balls in the bag is 15, and the number of red balls is 5. Therefore, the number of blue balls can be calculated as:
x + 5 = 15
x = 10
So, there are initially 10 blue balls in the bag.
The probability of drawing a blue ball is given by:
P(blue ball) = x/15
P(blue ball) = 10/15
P(blue ball) = 2/3
3. P(blue ball if 5 extra red balls are actually added):
If 5 extra red balls are added, the total number of red balls becomes 5 + 5 = 10.
The total number of balls in the bag becomes 15 + 5 = 20.
The probability of drawing a blue ball in this case can be calculated as:
P(blue ball if 5 extra red balls are added) = x/(x + 10)
P(blue ball if 5 extra red balls are added) = 10/20
P(blue ball if 5 extra red balls are added) = 1/2
Summary:
- The probability of drawing red balls is 1/3.
- The probability of drawing blue balls is 2/3.
- If 5 extra red balls are added, the probability of drawing a blue ball becomes 1/2.