Question

A person is asked to randomly pick two balls from a bag which has 15 red and 5 blue balls. The probability that the person picks two balls of the same colour is

Answer 1

I was never good with probability <.<
the way im thinking about it is:
(probability of picking 2 reds)+(probability of picking 2 blues)
\[(\frac{15}{20}*\frac{14}{19})+(\frac{5}{20}*\frac{4}{19}) = \frac{15*14+5*4}{380} = \frac{230}{380} = \frac{28}{38}\]

Answer 2

might be wrong though. like i said, probability isnt my strong suite.

Answer 3

Answer :- 23/38

Answer 4

oh my bad, typo:
\[\frac{230}{380} = \frac{23}{38}\]
at least i was correct lol >.<

Answer 5

Total sample space = 20C2 = 190
The number of ways of selecting 2 balls of same color from a suit of 15 red balls
15C2 = 105
The number of ways of selecting 2 balls of same color from a suit of 5 blue balls
5C2 = 10

Thus the probability that the person picks 2 balls of same color = [105/190 + 10/190]
= 115/190 = 23/38

Answer 6

ah i never would have thought of it that way, nice :)

Answer 7

actually, now that i look at it, thats what my calculations are lol

Answer 8

The question was there in one of the Aptitude test paper. :)