Can someone just tell me the formula to use for this problem?

Jack is taking a four item true/false test. He decides to flip a coin to answer. What is the probablility he gets a perfect score? What is the probablility on a 10 question test?

The probability of getting any one true-false item correct by chance = 1/2 = .5. To get the probability of all events occurring, you need to multiply the probability of the individual events.

four items = .5^4

10 items = .5^10