Question

A dies is thrown until a score of less than $5$ point is obtained. The probability of obtaining not less than $2$ points on the last throw is:

• A. $\frac{3}{4}$
• B. $\frac{1}{4}$
• C. $\frac{5}{8}$
• D. $\frac{2}{7}$

Answer 1

Answer: (A)

$\frac{3}{4}$

Total number of outcomes, $n\left(S\right)=6$

Hence, the probability of obtaining not less than 2 points on the last throw is $\frac{3}{6}+\frac{2}{6}\times \frac{3}{6}+\frac{2}{6}\times \frac{2}{6}\times \frac{3}{6}+...$

$⟹=\frac{\frac{1}{2}}{1-\frac{1}{3}}=\frac{1}{2}\times \frac{3}{2}=\frac{3}{4}$