Question

The mean of the numbers obtained on throwing a die having written 1 on three faces, 2 on two faces and 5 on one face is (A) 1 (B) 2 (C) 5 (D)

Answer 1

Let, the number on the die be represented by the random variable X.

A die has the total number of observations as six.

So,

P( X=1 )= 3 6 = 1 2

P( X=2 )= 2 6 = 1 3

P( X=5 )= 1 6

Therefore, the probability distribution is as follows:

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

Mean=E( X ) = ∑ X i P( X i ) = 1 2 ×1+ 1 3 ×2+ 1 6 ×5 = 12 6

Thus, the mean of the numbers is 2.

Therefore, the correct option is (B).