Question

A bag contains 20 balls out of which x balls are red. If one ball is drawn at random,
i) Find the probability of drawing a red ball.
ii) If 10 more red balls are put in the bag, then the probability of getting a red ball is double the probability obtained in (i). Find the value of x.

Answer 1

see this answer....................

Answer 2

I) probability of a drawing a red ball is equals to
no of red balls /20
$= \frac{x}{20}$
ii )now no of red balls =10+x
it is equal to double of probability we get in I

than
$\frac{10 + x}{30} = \frac{2x}{20}$
20(10+x)=30(2x)
200+20x=60x
200=60x--20x
200=40x
x=200/40
x=5