Question

a bag contains 5 red balls and some blue balls .if the probability of drawing a blue ball from the bag is thrice that of a red balls in the bags.

Answer 1

No. of red balls=5
Let no. of blue balls be x
Total balls=5+x
according to question,
x/5+x = 3 X 5/x+5
x=15
no. of blue balls=15
P(of blue ball)=15/20=3/4

Answer 2

Given

• The bag contains 5 red balls
• Some blue balls
• Also, it is given that the probability of drawing a blue ball is thrice of that of a red ball

To find

The number of blue balls in the bag

Solution

Let the number of blue balls be= x

So now we know that the total balls in the bag = 5+x

Therefore, the probability of drawing a blue ball =   $\frac{Number of blue balls}{Total number of balls}$

So the probablity of blue ball=     $\frac{x}{x+5}$-------- equation 1

The probability of red ball =         $\frac{5}{x+5}$--------- equation 2

Total number of blue balls = $\frac{x}{x+5}$ =3($\frac{5}{x+5}$)

We get the answer by cross multiplying it as 15

So the total number of the blue balls is 15