Question

a bag contains 6 white balls and 9 red balls and some blue balls and black balls

if probability of drawing white ball is double that of blue find the number of blue balls in the bag

if the probability of drawing a red ball is three times the probability of black ball, find number of black balls in the bag ​

Answer 1

Step-by-step explanation:

let the number of blue and black balls

be x and y respectively

probability of white ball

=6÷(15+x+y)

and probability of blue balls

=x÷(15+x+y)

by question

6÷(15+x+y)=2×x÷(15+x+y)

or 90+6x+6y=x(30+2x+2y)

x=3

again probability of red balls

9÷(15+x+y)

probability of black balls

3y÷(15+x+y)

by question

=9÷(15+x+y)=3×y÷(15+x+y)

or 135+9x+9y=y(45+3x+3y)

so y=3