Michael draws a card from a standard deck of 52 cards (and puts it back) 20 times.

How many times can Michael expect to draw a diamond?

1 answer

A standard deck of cards contains 52 cards, with 13 cards in each suit (hearts, diamonds, clubs, spades). Therefore, the probability of drawing a diamond in a single draw is:

\[ P(\text{diamond}) = \frac{\text{number of diamonds}}{\text{total number of cards}} = \frac{13}{52} = \frac{1}{4} \]

Michael draws a card 20 times, and we want to find the expected number of times he draws a diamond. The expected value \(E\) for a binomial distribution can be calculated using the formula:

\[ E = n \cdot p \]

where \(n\) is the number of trials (draws) and \(p\) is the probability of success (drawing a diamond).

In this case, we have:

  • \(n = 20\) (the number of draws)
  • \(p = \frac{1}{4}\) (the probability of drawing a diamond)

Now we can calculate the expected number of diamonds drawn:

\[ E = 20 \cdot \frac{1}{4} = 5 \]

Therefore, Michael can expect to draw a diamond 5 times.