Question

a beg contains 5 red ball and some blue balls. if the probability of drawing a blue ball is double than that of red ball determine the number of blue ball in the bag ​

Answer 1

Given:-

There are 5 red balls, the probability of drawing the blue ball is double than the red ball.

Required answer:-

The number of blue balls in the bag.

Solution:-

Number of red balls = 5

Let the number of blue balls be x,

∴ total number of balls = 5 + x

$\bf{Probability\: of \:red \:ball }=\bf\frac{Number\: of \:red\: balls}{Total\: number\:of \:balls} =\frac{5}{5 +x}$

$\therefore\bf{Probability\:of\:blue\:ball=\frac{5}{5+x} .2 = \frac{10}{5+x} }$

$\bf{Now,\:sum\:of\:probabilities=1}$

$\implies\bf{\frac{10}{5+x} +\frac{5}{5+x} =1}$

$\implies\bf{\frac{15}{5+x} =1}$

$\implies\bf{15=5+x}$

$\implies\bf{x=15-5}$

$\therefore\bf{x = 10}$

hence, number of blue balls = 10