A box contains 5 red and 3 green marbles. If one marble is drawn and it is red,

Practice Questions

Q1
A box contains 5 red and 3 green marbles. If one marble is drawn and it is red, what is the probability that the next marble drawn is green?
  1. 3/7
  2. 2/7
  3. 1/7
  4. 1/3

Questions & Step-by-Step Solutions

A box contains 5 red and 3 green marbles. If one marble is drawn and it is red, what is the probability that the next marble drawn is green?
Correct Answer: 3/7
  • Step 1: Start with the total number of marbles in the box. There are 5 red marbles and 3 green marbles.
  • Step 2: Calculate the total number of marbles. 5 red + 3 green = 8 marbles in total.
  • Step 3: Draw one marble from the box. If the marble drawn is red, we remove it from the box.
  • Step 4: After drawing one red marble, count the remaining marbles. There are now 4 red marbles left and still 3 green marbles.
  • Step 5: Calculate the new total number of marbles left in the box. 4 red + 3 green = 7 marbles left.
  • Step 6: Now, find the probability of drawing a green marble next. There are 3 green marbles left out of 7 total marbles.
  • Step 7: The probability of drawing a green marble is 3 (green marbles) divided by 7 (total marbles), which is 3/7.
  • 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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