Nico uses a uniform probability model for an experiment using a deck of 40 cards. There are 10 blue cards, 10 red cards, 10 green cards, and 10 yellow cards in the deck. Cards will be drawn one at a time and then replaced in the deck before another card is drawn.
He uses the probability model to determine the probability of drawing a green card or a red card.
What is P(green or red)?
Enter your answer as a simplified fraction in the box.
The probability of drawing a green card or a red card can be calculated by adding the individual probabilities of drawing a green card and drawing a red card, and then subtracting the probability of drawing both a green and red card simultaneously (which is 0 since the cards are replaced after each draw).
P(green or red) = P(green) + P(red) - P(green and red)
P(green) = 10/40 = 1/4
P(red) = 10/40 = 1/4
P(green and red) = 0
Therefore, P(green or red) = 1/4 + 1/4 - 0 = 1/2
So, the probability of drawing a green card or a red card is 1/2.