A bag contains 5 black, 7red and 3 white balls. A ball is drawn from the bag at random. Find the probability that the ball drawn is :
(i) red
(ii) black or white
(iii) not black
GIVEN: A bag contains 7 red, 5 black and 3 white balls and a ball is drawn at random
TO FIND: Probability of getting a
(i) Red ball
(ii) Black or white ball
(iii) Not black ball
Total number of balls 
(i) Total number red balls are 7
We know that PROBABILITY = 
Hence probability of getting a red ball is equal to
(ii) Total number of black or white balls is 
We know that PROBABILITY =
Hence probability of getting white or black ball 
(iii) Total number of black balls is 5
We know that PROBABILITY =
Hence probability of getting black ball 
We know that sum of probability of occurrence of an event and probability of non
occurrence of an event is 1
$P(E)+P(\bar{E})=1$
$\frac{1}{3}+P(\bar{E})=1$
$P(\bar{E})=1-\frac{1}{3}$
$P(\bar{E})=\frac{2}{3}$
Hence the probability of getting non black ball $P(\bar{E})=\frac{2}{3}$