Math Problem Statement

A number is randomly selected from the set of all numbers x where 7/8 <= x <= 4/3. What is the probability that the number will be greater than or equal to 1?

Solution

Let's solve the problem step-by-step:

We are asked to find the probability that a randomly selected number from the set 78x43\frac{7}{8} \leq x \leq \frac{4}{3} is greater than or equal to 1.

Step 1: Define the range

The range of numbers is 78x43\frac{7}{8} \leq x \leq \frac{4}{3}. We need to split this range into two parts:

  • Numbers less than 1 (but greater than or equal to 78\frac{7}{8}).
  • Numbers greater than or equal to 1 (but less than or equal to 43\frac{4}{3}).

Step 2: Length of total interval

The total range of numbers is from 78\frac{7}{8} to 43\frac{4}{3}.

To find the length of this interval: Total length=4378\text{Total length} = \frac{4}{3} - \frac{7}{8} We need to get a common denominator: 43=3224,78=2124\frac{4}{3} = \frac{32}{24}, \quad \frac{7}{8} = \frac{21}{24} Total length=32242124=1124\text{Total length} = \frac{32}{24} - \frac{21}{24} = \frac{11}{24}

Step 3: Length of interval where x1x \geq 1

Now, we need to find the length of the interval where x1x \geq 1, that is, from 1 to 43\frac{4}{3}: Length where x1=431=4333=13\text{Length where } x \geq 1 = \frac{4}{3} - 1 = \frac{4}{3} - \frac{3}{3} = \frac{1}{3}

Step 4: Probability

The probability is the ratio of the interval where x1x \geq 1 to the total interval length: Probability=131124=13×2411=811\text{Probability} = \frac{\frac{1}{3}}{\frac{11}{24}} = \frac{1}{3} \times \frac{24}{11} = \frac{8}{11}

Thus, the probability that the randomly selected number will be greater than or equal to 1 is 811\boxed{\frac{8}{11}}, which corresponds to option (D).


Would you like further details or have any questions? Here are some related questions to consider:

  1. What is the concept of probability in continuous intervals?
  2. How do you find the length of intervals on the real number line?
  3. How can common denominators help in subtracting fractions?
  4. What is the meaning of probability as a ratio of lengths?
  5. How does this problem differ from finding probabilities for discrete sets?

Tip: Always ensure to break down complex ranges into simpler intervals when dealing with probabilities in continuous sets.

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Math Problem Analysis

Mathematical Concepts

Probability
Continuous Probability
Intervals on a Number Line

Formulas

Length of an interval = upper bound - lower bound
Probability = favorable interval / total interval

Theorems

Basic Probability Theorem

Suitable Grade Level

Grades 10-12