Q. Let $A = \left\{ 1,\ 3,\ 5,\ 7,\ 9 \right\},\ B = \left\{ 2,\ 4,\ 6,\ 8 \right\}.$ If a cartesian product $A \times B$, if chosen at random, the probability of $a + b = 9$ is

A) $\frac{1}{4}$
B) $\frac{1}{5}$
C) 1
D) 0
Explanation

(b)
Total number of cases=20
Favorable cases=$\left\{ (1,8),(3,6),(5,4),(7,2) \right\} = 4$
$\therefore$ Required probability $= \frac{4}{20} = \frac{1}{5}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.