Question

A pair of unbiased dice is thrown once. Let $X$ be the random variable denoting the product of numbers that appear on the two dice. Then $P\left(X \ge21\right)=$

• A. $\frac{5}{36}$
• B. $\frac{7}{36}$
• C. $\frac{1}{6}$
• D. $\frac{1}{12}$

Answer 1

Answer: (C)

$\frac{1}{6}$

Answer 2

Let $A$ be the event such that the product of the numbers is greater than or equal to $21$.
$\therefore A = \\{(4,6), (5,5), (5,6), (6,4), (6,5), (6,6)\\}$
Required probability $= \frac{6}{36}$
$= \frac{1}{6}$