Question

A bag contains 5 red balls and some Blue Balls if the probability of drawing a blue ball is double that of a red ball determine the number of blue balls in the bag

Answer 1

Heya☺

Total no.of balls = 5 + b (blue balls)

Probability = No. of favourable outcomes/total no. of outcomes


According to question

P(b) = 2P(R)
b/5+b = 2(5/5+b)

b =10
Hence no.of blue balls is 10✌

Answer 2

Solution :

Let there be x blue balls in the bag.

∴ Total number of balls in the bag = 5 + x

Now,

          $p_{1}$ = Probability of drawning a blue ball = $\frac{x}{5 + x}$

          $p_{2}$ = Probability of drawing a red ball = $\frac{5}{5 + x}$

But it is given that $P_{1}$ = $2p_{2}$

⇒ $\frac{x}{5 + x}$ = $2 \times \frac{5}{5 + x}$

⇒ x = 10