A box contains 4 red, 3 green, and 5 blue balls. If a ball is drawn and it is bl

Practice Questions

Q1
A box contains 4 red, 3 green, and 5 blue balls. If a ball is drawn and it is blue, what is the probability that the next ball drawn is red?
  1. 4/11
  2. 3/11
  3. 5/11
  4. 1/3

Questions & Step-by-Step Solutions

A box contains 4 red, 3 green, and 5 blue balls. If a ball is drawn and it is blue, what is the probability that the next ball drawn is red?
Correct Answer: 4/11
  • Step 1: Count the total number of balls in the box. There are 4 red, 3 green, and 5 blue balls. So, total = 4 + 3 + 5 = 12 balls.
  • Step 2: Draw one blue ball from the box. Now, we have 4 red, 3 green, and 4 blue balls left.
  • Step 3: Count the remaining balls. After drawing one blue ball, the total number of balls left is 4 red + 3 green + 4 blue = 11 balls.
  • Step 4: Determine how many red balls are left. There are still 4 red balls left.
  • Step 5: Calculate the probability of drawing a red ball next. The probability is the number of red balls divided by the total number of remaining balls: Probability = 4 red / 11 total = 4/11.
  • Conditional Probability – The probability of an event occurring given that another event has already occurred.
  • Counting Outcomes – Understanding how to count the remaining outcomes after an event has taken place.
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