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