Question

A single dice is thrown twice. What is the probability that the sum is neither 8 nor 9?

• A. 1/9
• B. 5/36
• C. 1/4
• D. 3/4

Answer 1

The correct option is D 3/4

A single die is thrown twice.
A sum of 8 can be obtained as follows

(2, 6), (3, 5), (4, 4), (5, 3), (6, 2)

Probability of getting sum 8$=\frac{5}{6^2}=\frac{5}{36}$

A sum of 9 can be obtained as follows
(3, 6), (4, 5), (5, 4), (6, 3)

Probability of getting sum 9
$=\frac{4}{36}$

Probability that the sum is neither 8 nor 9 = 1 - P(sum is either 8 or 9)

$=1-(\frac{5}{36}+\frac{4}{36})=\frac{3}{4}$