Q. A bag contain 5 black balls, 4 white balls and 3 red balls. If a ball is selected randomly, the probability that it is a black or red ball, is
A) 1/3
B) $1/4$
C) 5/12
D) 2/3
Explanation
(d)
$P$ (selecting a black ball) $= \frac{{\ ^{5}C}_{1}}{{\ ^{12}C}_{1}}$
$P$ (selecting a red ball)$= \frac{{\ ^{3}C}_{1}}{{\ ^{12}C}_{1}}$
$P$ (black ball or red ball) $= \frac{{\ ^{5}C}_{1} + {\ ^{3}C}_{1}}{{\ ^{12}C}_{1}} = \frac{2}{3}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.