There are a total of $6\cdot6=36$ possible outcomes when rolling the two cubes. We want to count the number of outcomes that have a sum of 9. We can organize these outcomes in a table:
\begin{tabular}{|c|c|c|c|c|c|}
\hline
1+8 & 2+7 & 3+6 & 4+5 & 5+4 & 6+3 \\
\hline
7+2 & 8+1 & & & & \\
\hline
\end{tabular}
We have listed all possible outcomes with a sum of 9. We can count a total of 8 outcomes, out of 36 possible outcomes, that have a sum of 9. Therefore, the probability of rolling a sum of 9 is $\boxed{\textbf{(B) } \frac19}$.
William has a pair of identical number cubes. The faces of each cube are numbered 1 through 6. William will roll the cubes one time. What is the probability that the numbers showing face-up after the roll will have a sum of 9?
A. Start Fraction 1 over 18 End Fraction
B. start fraction 1 over 9 end fraction
C. three-fourths
D. start fraction 8 over 9 end fraction.
1 answer