Question:
Cards bearing numbers 2, 3, 4, ..., 11 are kept in a bag. A card is drawn at random from the bag. The probability of getting a card with a prime number is
(a) $\frac{1}{2}$
(b) $\frac{2}{5}$
(C) $\frac{3}{10}$
(d) $\frac{5}{9}$
Solution:
Total number of cards = 10.
Out of the given numbers, prime numbers are 2, 3, 5, 7 and 11.
Numbers of favourable outcomes = 5.
$\therefore \mathrm{P}$ (getting a prime number) $=\frac{\text { Number of favourable outcomes }}{\text { Number of all possible outcomes }}$
$=\frac{5}{10}=\frac{1}{2}$
Thus, the probability of getting a card with a prime number is $\frac{1}{2}$.
Hence, the correct answer is option (a).