Q. Six faces of an unbiased die are numbered with 2, 3, 5, 7, 11 and 13. If two such dice are thrown, then the probability that the sum on the uppermost faces of the dice is an odd number, is
A) $\frac{5}{18}$
B) $\frac{5}{36}$
C) $\frac{13}{18}$
D) $\frac{25}{36}$
Explanation
(a)
The sum of two numbered on a dice is odd only, whence once is odd and second is even.
$\therefore$ Required probability
$= 2 \times$probability of odd number
$\times$probability of even number
$\lbrack\because$Here, we multiply by 2 because either the even number is on first or second dice.]
$= 2 \times \left( \frac{5}{6} \right) \times \left( \frac{1}{6} \right) = \frac{5}{18}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.