Math Problem Statement

In a garden, 40% of the flowers are roses and the rest are carnations. If 25% of the roses and 10% of the carnations are red, find the probability that a red flower selected at random is a rose.

Solution

This problem requires the application of Bayes' Theorem to find the probability that a randomly selected red flower is a rose. We are given:

  • 40% of the flowers are roses, meaning P(Rose)=0.40P(\text{Rose}) = 0.40 and the rest are carnations, so P(Carnation)=0.60P(\text{Carnation}) = 0.60.
  • 25% of the roses are red, meaning P(RedRose)=0.25P(\text{Red} \mid \text{Rose}) = 0.25.
  • 10% of the carnations are red, meaning P(RedCarnation)=0.10P(\text{Red} \mid \text{Carnation}) = 0.10.

Step 1: Calculate the total probability of selecting a red flower.

We use the Law of Total Probability to compute P(Red)P(\text{Red}), the probability that a flower is red:

P(Red)=P(RedRose)P(Rose)+P(RedCarnation)P(Carnation)P(\text{Red}) = P(\text{Red} \mid \text{Rose}) P(\text{Rose}) + P(\text{Red} \mid \text{Carnation}) P(\text{Carnation})

Substitute the values:

P(Red)=(0.25×0.40)+(0.10×0.60)P(\text{Red}) = (0.25 \times 0.40) + (0.10 \times 0.60) P(Red)=0.10+0.06=0.16P(\text{Red}) = 0.10 + 0.06 = 0.16

Step 2: Use Bayes' Theorem to find the probability that a red flower is a rose.

Bayes' Theorem is given by:

P(RoseRed)=P(RedRose)P(Rose)P(Red)P(\text{Rose} \mid \text{Red}) = \frac{P(\text{Red} \mid \text{Rose}) P(\text{Rose})}{P(\text{Red})}

Substitute the known values:

P(RoseRed)=0.25×0.400.16P(\text{Rose} \mid \text{Red}) = \frac{0.25 \times 0.40}{0.16} P(RoseRed)=0.100.16=0.625P(\text{Rose} \mid \text{Red}) = \frac{0.10}{0.16} = 0.625

Thus, the probability that a randomly selected red flower is a rose is 0.625 or 62.5%.


Would you like further details or have any questions?

Related Questions:

  1. How would the problem change if 50% of the flowers were roses?
  2. What is the probability that a flower selected at random is red?
  3. How does Bayes' Theorem work in general cases?
  4. What happens if 100% of the roses were red?
  5. How would you modify the problem if there were a third type of flower in the garden?

Tip:

Bayes' Theorem is a powerful tool for updating probabilities based on new evidence, and it's widely used in areas like statistics, machine learning, and decision-making.

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Math Problem Analysis

Mathematical Concepts

Probability
Conditional Probability
Bayes' Theorem

Formulas

P(Red) = P(Red | Rose) * P(Rose) + P(Red | Carnation) * P(Carnation)
Bayes' Theorem: P(Rose | Red) = [P(Red | Rose) * P(Rose)] / P(Red)

Theorems

Bayes' Theorem
Law of Total Probability

Suitable Grade Level

Grades 9-12