A bag contains 5 red balls and some blue balls. If the probability of drawing a blue ball is double that of a red ball , determine the number of blue balls in the bag. (Ans:10)
Ans: Let the number of blue balls is the bag be x
Then total number of balls is the bag = 5 + x
∴ Number of all possible outcomes = 5 + x
Number of outcomes favourable to the event of drawing a blue ball = x
(Q there are x blue balls)
∴ Probability of drawing a blue ball x/ 5 + x
Similarly, probability of drawing a red ball = 5/5 + x
According to the answer
x/5 + x = 2(5/5+x)
x = 10