Math Problem Statement

You pick a card at random, put it back, and then pick another card at random.

2 3 4 5 6 7 8

What is the probability of picking an 8 and then picking a number greater than 4?

Write your answer as a fraction or whole number.

Solution

To solve this, we need to calculate the probability of two events happening in sequence:

  1. First, picking an 8:
    There is 1 card with an 8 in the set {2, 3, 4, 5, 6, 7, 8}, so the probability of picking an 8 is:
    P(8)=17P(\text{8}) = \frac{1}{7}

  2. Second, picking a number greater than 4:
    The numbers greater than 4 in this set are {5, 6, 7, 8}, so there are 4 favorable outcomes. The probability of picking a number greater than 4 is:
    P(> 4)=47P(\text{> 4}) = \frac{4}{7}

Since these two events are independent (you replace the card after each pick), the total probability of both events happening is the product of the individual probabilities: P(8 and > 4)=P(8)×P(> 4)=17×47=449P(\text{8 and > 4}) = P(\text{8}) \times P(\text{> 4}) = \frac{1}{7} \times \frac{4}{7} = \frac{4}{49}

Thus, the probability of picking an 8 and then picking a number greater than 4 is 449\frac{4}{49}.


Would you like further details or have any other questions? Here's some related questions for you:

  1. What is the probability of picking a 6 and then picking a number less than 6?
  2. If there were two 8s in the deck, how would that affect the probability of picking an 8 first?
  3. How would the probability change if there were 10 cards in total instead of 7?
  4. What is the probability of picking two numbers greater than 4 consecutively?
  5. What is the probability of picking a card smaller than 5 and then a card smaller than 3?

Tip: When dealing with independent events (like picking cards with replacement), you can always multiply the probabilities of each event occurring.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Probability
Independent Events

Formulas

P(A and B) = P(A) × P(B)

Theorems

Multiplication Rule for Independent Events

Suitable Grade Level

Grades 7-9