Question

A bag contains 18 balls out of which x balls are red

(i) If one ball is drawn at random from the bag, then what is the probability that it is a red ball?
(ii) If 2 more red balls are put in the bag then probability of drawing a red ball will be $\frac{9}{8}$ time that of probability of red ball coming in part , find the value of x.

Answer 1

bag contains $=18$ balls

no. of red balls $=x$

Probability of red ball $=\frac{Favourableball}{totalnoofball}$

$\left(i\right)P\left[redball\right]=\frac{x}{18}$

$\left(ii\right)$ If two more red ball add

no. of red ball $=x+2$

total no. of balls $=18+2=20$

Probability of druuing red ball $=\frac{9}{8}$ Probability of red ball coming in part $\left(i\right)$

$\therefore \frac{x+2}{20}=\frac{9}{8}\times \frac{x}{18}$

$\therefore \frac{x+2}{20}=\frac{x}{16}$

$\therefore 16(x+2)=20x$

$\therefore 16x+32=20x$

$\therefore 20x-16x=32$

$\therefore 4x=32$

$\therefore x=8$

$\to$ the value of $x=8$