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:-

Options

• 1

• 2

• 5

• `8/3`

Answer 1

2

Explanation:

The Variables are 1, 2 and 5

1 is written on 3 faces.

∴ Probability of getting 1 = `3/6 = 1/2`

2 is written on two faces

∴ Probability of getting 2 = `2/6 = 1/3`

5 is written on 1 faces

∴ Probability of getting 5 = `1/6`

Probability distribution is

X	1	2	5
P(x)	`1/2`	`1/3`	`1/16`

Mean = E(x) = `sumP_iX_i = 1/2 xx 1 + 1/3 xx 2 + 1/6 xx 5`

= `1/2 + 2/3 + 5/6`

= `(3 + 4 + 5)/6`

= `1/6`

= 2