To find the probability of selecting the letter "C" or the coin landing tails up, we need to calculate the probability of each event individually and then add the probabilities of the two events together.
The probability of selecting the letter "C" is:
1/5
This is because there are 5 letters in total, A, B, C, D, and E, and "C" is one of them, so the probability of selecting "C" is 1/5.
The probability of the coin landing tails up is:
1/2
This is because there are two possible outcomes when flipping a coin, heads or tails, and since the coin is fair, the probability of getting heads or tails is 1/2.
To find the combined probability of the two events we need to add them together using the rule of "or" in probability which is defined as:
P(A or B) = P(A) + P(B) - P(A and B)
However in this case A and B are mutually exclusive events, meaning they can't happen at the same time. There is no way to have "C" and coin landing tails up at the same time. Then we don't have to subtract P(A and B)
Therefore, the probability of selecting the letter "C" or the coin landing tails up is:
1/5 + 1/2 = 2/5 + 1/2 = 7/10
So the probability of selecting the letter "C" or the coin landing tails up is 7/10