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A 12-sided solid has equal-sized faces numbered 1 to 12.

a. Find [tex]P(\text{number greater than 10})[/tex].

b. Find [tex]P(\text{number less than 5})[/tex].


Sagot :

Certainly! Let's tackle each part of the question step-by-step.

We have a 12-sided solid (or die) with faces numbered from 1 to 12. Since all faces are equal in size, each number has an equal probability of being rolled.

### Part (a): Find the Probability of Rolling a Number Greater than 10

1. Identify Favorable Outcomes:
Numbers greater than 10 on a 12-sided die are 11 and 12. So there are 2 favorable outcomes.

2. Total Possible Outcomes:
There are 12 faces on the die, so there are 12 possible outcomes.

3. Calculate Probability:
The probability [tex]\( P \)[/tex] of rolling a number greater than 10 is given by the ratio of favorable outcomes to the total outcomes:
[tex]\[ P(\text{number greater than 10}) = \frac{\text{favorable outcomes}}{\text{total outcomes}} = \frac{2}{12} \][/tex]

4. Simplify the Fraction:
[tex]\[ \frac{2}{12} = \frac{1}{6} \approx 0.1667 \][/tex]

So, the probability of rolling a number greater than 10 is approximately 0.1667 (or [tex]\( \frac{1}{6} \)[/tex]).

### Part (b): Find the Probability of Rolling a Number Less than 5

1. Identify Favorable Outcomes:
Numbers less than 5 on a 12-sided die are 1, 2, 3, and 4. So there are 4 favorable outcomes.

2. Total Possible Outcomes:
Again, there are 12 faces on the die, so there are 12 possible outcomes.

3. Calculate Probability:
The probability [tex]\( P \)[/tex] of rolling a number less than 5 is given by the ratio of favorable outcomes to the total outcomes:
[tex]\[ P(\text{number less than 5}) = \frac{\text{favorable outcomes}}{\text{total outcomes}} = \frac{4}{12} \][/tex]

4. Simplify the Fraction:
[tex]\[ \frac{4}{12} = \frac{1}{3} \approx 0.3333 \][/tex]

So, the probability of rolling a number less than 5 is approximately 0.3333 (or [tex]\( \frac{1}{3} \)[/tex]).

### Notes on Expectation:

The phrase "expect either a 4, 6, or 9 to be rolled" appears ambiguous in the question context unless further qualified. If the question is part of the original prompt, then it might be asking for expectations in a different scenario, unrelated to probability calculations directly here. Rolling either a 4, 6, or 9 would have a different set of considerations.

To summarize:

- The probability of rolling a number greater than 10 is 0.1667.
- The probability of rolling a number less than 5 is 0.3333.