(i) The probability of an even card is 1/2 because the number of even cards and odd cards are the same so there is a 50% of getting an even card. (b)
(ii) Since the card is replaced, there is still a card for all numbers between 1-20. There are 8 prime numbers and 20 cards so the probability of getting a prime number is 8/20 or 4/10 or 2/5. (a)
(iii) The card was not replaced so there are only 19 cards and there are only 5 numbers that are multiples of 3 and greater than 4. The probability must be 5/19. (d)
(iv) A sure event means that it will happen 100%. So P(A) = 1 since the number one represents 100%. (a)
(v) All cards have replaced and there is only one number that is a multiple of 3 and 5 which is 15. 1 card out of 20 is a desired outcome so 1/20 is the probability. (c)
