Question

In a random experiment, a fair die is rolled until two fours are obtained in succession. The probability that the experiment will end in the fifth throw of the die is equal to :

• A. $\frac{150}{6^5}$
• B. $\frac{175}{6^5}$
• C. $\frac{200}{6^5}$
• D. $\frac{225}{6^5}$

Answer 1

Answer: (B)

$\frac{175}{6^5}$

Answer 2

$\underline{ } \underline{ } \underline{ } \underline{4 } \underline{ 4}$
$\frac{1}{6^{2} } \left( \frac{5^{3}}{6^{3}} + \frac{2C_{1}.5^{2}}{6^{3}}\right) = \frac{175}{6^{5}}$