GATE Electrical 2014 Set 2 | Question: 2

Question

Consider a dice with the property that the probability of a face with $n$ dots showing up is proportional to $n$. The probability of the face with three dots showing up is ________.

Answer 1

X	1	2	3	4	5	6
P(X)	k	2k	3k	4k	5k	6k

where, k is a proportional constant.

∑P(X)=1

k+2k+3k+4k+5k+6k = 1

k= 1/21

P(3 dots) = 3* 1/21 =3/21 (Answer)

Comments

Why we are equating it to 1

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Because summation of any random event is always equal to 1 in probability

Probability of having an event+ probability of not having an event =1

p+ ~p = 1