A pair of fair dice is tossed repeatedly until a sum of four... | Mathematics | SolveeIt | Solveeit

Today, August 18

Question

A pair of fair dice is tossed repeatedly until a sum of four or an odd sum appears. Then the probability that a sum of four appears first is

A

$\frac{1}{3}$

B

$\frac{2}{5}$

C

$\frac{3}{8}$

D

$\frac{1}{7}$

Answer

$\frac{1}{7}$

Explanation

Solution

The number of result of pair of dice which sum of $4$ is $3$ . The number of result of a pair of dice which odd sum is $18$ . The probability the sum $4$ appear before the odd sum is $= \frac{3}{3+18} = \frac{3}{21} = \frac{1}{7}$