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Two dice are tossed, one after the other. In how many different ways can they fall? List the number of different ways the sum of the dots can equal (a) 3 (b) 5 (c) 7 (d) 9 (e) 11

Short Answer

Expert verified
(a) 2 ways, (b) 4 ways, (c) 6 ways, (d) 4 ways, (e) 2 ways.

Step by step solution

01

Calculate Total Possible Outcomes

When two dice are tossed, each die has 6 faces that can show different numbers ranging from 1 to 6. To find the total number of possible outcomes, multiply the number of outcomes of the first die by the number of outcomes of the second die: \(6 \times 6 = 36\). Hence, there are 36 different ways the dice can fall.
02

Find Combinations for Sum of 3

To obtain a sum of 3, the pairs of numbers on the dice can be:\( (1, 2) \) and \( (2, 1) \). Verify that these add to 3 and ensure you include all orders. Thus, there are 2 combinations for the sum of 3.
03

Find Combinations for Sum of 5

For the sum to be 5, list pairs such as: \( (1, 4), (2, 3), (3, 2), \) and \( (4, 1) \). Check each pair to ensure their sum is 5. Thus, there are 4 combinations where the sum of dots is 5.
04

Find Combinations for Sum of 7

To get a sum of 7, the pairs are: \( (1, 6), (2, 5), (3, 4), (4, 3), (5, 2), \) and \( (6, 1) \). Verify each pair adds to 7. So, there are 6 combinations producing a sum of 7.
05

Find Combinations for Sum of 9

Pairs that add up to 9 are: \( (3, 6), (4, 5), (5, 4), \) and \( (6, 3) \). Confirm each pair results in a sum of 9. This provides 4 combinations where the sum is 9.
06

Find Combinations for Sum of 11

Pairs yielding a sum of 11 are: \( (5, 6) \) and \( (6, 5) \). Confirm these combinations add to 11. Hence, there are 2 ways to achieve a sum of 11.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Combinatorics
Combinatorics is a branch of mathematics that deals with counting, arrangement, and combination of objects. It's a tool that helps us determine the number of possible configurations in a given situation. When dealing with dice, combinatorics helps us count the various outcomes and configurations with each roll.

To solve problems involving probability, we often use combinatorics to calculate how many ways certain results can happen. The outcome of rolling two dice is a classic example. Here, we calculate the total number of outcomes and specific outcomes, such as how many ways the dice can sum to a particular number. By understanding these arrangements, we can tackle more complex problems that rely on the foundational principles of combinatorics.

Thus, combinatorics provides a clearer picture of possibilities, making it easier to estimate probabilities accurately for various scenarios.
Dice outcomes
When two dice are rolled, they each have six faces numbered from 1 to 6, creating a total of 36 different outcomes. These 36 outcomes consist of ordered pairs where the outcome from the first die is paired with the outcome from the second die. For instance, rolling a 1 on the first die and a 2 on the second die is different from rolling a 2 on the first die and a 1 on the second. This distinction is key to understanding the total number of dice outcomes and is why tossing two dice gives more combinations than tossing just one dice twice.

Understanding these outcomes aids in calculating how likely certain sums or sequences are. The basic comprehension of all possible outcomes assists in determining permutations and combinations more efficiently, which play a crucial role in solving probability problems associated with dice.
Sum of two dice
Calculating the sum of two dice involves identifying all the pairs that result in a particular sum. Each sum can occur through various combinations of numbered faces from both dice. For example, to get a sum of 7, you could roll (1,6), (2,5), (3,4), and similarly, the reverse pairs such as (6,1).

Here's how to find the sums:
  • Identify possible combinations: Write down all pairs of numbers that total the desired sum.
  • Verify each: Calculate the sum of each pair to ensure it matches the desired total.
This method provides a systematic way of listing outcomes where dice add up to a specific number, aiding in probability calculations associated with these sums.
Permutations and combinations
Permutations and combinations are fundamental concepts in probability and combinatorics. With two dice rolling, we often look at combinations since the order of numbers does not change the sum. For instance, a roll of (3,4) and (4,3) both result in a sum of 7. Here, combination tells us the group's count without considering order.

Permutations, in contrast, are used when order matters. With dice, this isn't typically necessary, as we are focused more on sum outcomes rather than sequence. But permutations still play a role in arranging outcomes in a specific way, should the need arise in more complex problems.

In essence, properly distinguishing between when to use permutations or combinations can simplify how we resolve probability questions, especially when multiple dice or complex sequences are in play.

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