To determine the probability of getting a sum less than 9 when rolling two six-sided dice, we need to follow these steps:

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1. Total Possible Outcomes

Each die has 6 faces, and rolling two dice gives:
$6 \times 6 = 36 \text{ possible outcomes}.$

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2. Favorable Outcomes (Sum < 9)

We now count all outcomes where the sum of the two dice is less than 9.

The possible sums for two dice range from 2 to 12. The favorable sums are:
$2, 3, 4, 5, 6, 7, 8$

We calculate how many outcomes correspond to each sum:

Sum	Outcomes (Ordered Pairs)	Count
2	(1,1)	1
3	(1,2), (2,1)	2
4	(1,3), (2,2), (3,1)	3
5	(1,4), (2,3), (3,2), (4,1)	4
6	(1,5), (2,4), (3,3), (4,2), (5,1)	5
7	(1,6), (2,5), (3,4), (4,3), (5,2), (6,1)	6
8	(2,6), (3,5), (4,4), (5,3), (6,2)	5

Adding up the counts:

$1 + 2 + 3 + 4 + 5 + 6 + 5 = 26$

So, there are 26 favorable outcomes where the sum is less than 9.

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3. Probability of Sum < 9

The probability is the ratio of favorable outcomes to the total outcomes:

$P(\text{Sum} < 9) = \frac{\text{Favorable Outcomes}}{\text{Total Outcomes}} = \frac{26}{36}$

Simplify the fraction:

$P(\text{Sum} < 9) = \frac{13}{18}$

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Final Answer:

The correct choice is:

D. $\frac{13}{18}$

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Follow-Up:

Would you like a more detailed explanation of how I listed the outcomes? Or do you need help with similar probability problems?

Here are 5 related questions you might consider:

1. What is the probability of getting a sum of exactly 7 when rolling two dice?
2. What is the probability of getting a sum greater than 9 when rolling two dice?
3. How many outcomes produce a sum of exactly 10 when two dice are rolled?
4. What is the probability of getting doubles (e.g., both dice show the same number)?
5. If three dice are rolled, what is the probability of getting a sum less than 10?

Tip: For dice problems, always start by listing the total possible outcomes to calculate probabilities accurately!