The mean of numbers obtained by throwing a die having 1 on three faces and 2 on two faces and 5 on one face is:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 2
Let X be the number obtained. Each of the 6 faces is equally likely, so
\( \displaystyle P(X = 1) = \frac{3}{6},\quad P(X = 2) = \frac{2}{6},\quad P(X = 5) = \frac{1}{6} \)
The mean is the expected value \(E(X) = \sum x\,P(X = x)\):
\( \displaystyle E(X) = 1 \times \frac{3}{6} + 2 \times \frac{2}{6} + 5 \times \frac{1}{6} \)
\( \displaystyle = \frac{3 + 4 + 5}{6} = \frac{12}{6} = 2 \)
CBSE Applied Mathematics (Class XII):
Probability Distribution
