Probability - General Questions

3 unbiased coins are tossed together. What is the probability of getting at least one head?

4 unbiased coins are tossed together. What is the probability of getting at least one head?

A letter is chosen at random from the word 'ORANGE'. What is the probability that it is a vowel?

A bag contains 7 red, 3 blue and 1 green ball. Two balls are drawn at random. What is the probability that both are red?

One card is drawn at random from a well-shuffled pack of 52 cards. What is the probability that it is a heart?