Question

There are $30$ blue balls and $x$ red balls in a bag. A ball is drawn at random from the bag.
Write down, in terms of $x$ an expression for the probability that the ball drawn is red.

Answer 1

No. of blue balls $=30$

No. of red balls $=x$

Total no. of balls $=x+30$

Prob. of getting red ball

$=\frac{x}{x+30}$