Question

A bag contains 5 red balls and some Blue Balls if the probability of drawing blue ball is thrice that of red ball. Find the number of ball in the bag

Answer 1

5×3+5=20 I think is the answer

Answer 2

Let the number of blue balls be 'x' 
And the number of red balls is 5
Then the total number of balls = 5+x

Then P(drawing a blue ball) = 3× {P(drawing a red ball)}

No. of blue balls ÷ total no. of balls  =  3× no. of red balls ÷ total no. of balls

x ÷ 5+x = 3 × 5 ÷ 5 + x

solve it and the value of x = 15

Hope it helps  :)