A bag contains 16 blue marbles, 12 red marbles, and 12 green marbles. If Malik randomly draws a marble from the bag (and puts it back) 25 times, how many times should he expect to pull a blue marble?

1 answer

To find the expected number of times Malik will draw a blue marble, we first need to calculate the total number of marbles in the bag.

The bag contains:

  • 16 blue marbles
  • 12 red marbles
  • 12 green marbles

Total number of marbles = 16 + 12 + 12 = 40 marbles.

Next, we calculate the probability of drawing a blue marble. The probability \( P(\text{Blue}) \) is given by the formula:

\[ P(\text{Blue}) = \frac{\text{Number of blue marbles}}{\text{Total number of marbles}} = \frac{16}{40} = \frac{2}{5}. \]

Now, since Malik draws a marble 25 times, the expected number of times he will draw a blue marble can be calculated using the expected value formula:

\[ E(\text{Number of blue marbles drawn}) = \text{Number of draws} \times P(\text{Blue}) = 25 \times \frac{2}{5}. \]

Calculating that gives:

\[ E(\text{Number of blue marbles drawn}) = 25 \times \frac{2}{5} = 25 \times 0.4 = 10. \]

Thus, Malik should expect to pull a blue marble 10 times on average.