Checkpoint: coins, cards, numbers and draws

Three coins are tossed together. How many results are there, and what is P(three tails)?

• 6 results, P = 1/6
• 4 results, P = 1/4
• 8 results, P = 1/8

One card is drawn from a pack of 52. How many cards are face cards?

• 16
• 12
• 3

Tickets are numbered 1 to 12. What is P(a prime number)?

• 5/12
• 6/12 = 1/2
• 4/12 = 1/3

A bag has 2 red and 3 black balls. One black ball is kept out. What is P(the next ball is black)?

• 3/5
• 2/5
• 2/4 = 1/2

Three coins are tossed. A student says P(exactly one head) = 1/4, because there are 4 head-groups. What is wrong?

• The 4 groups hold 1, 3, 3 and 1 results.
• There are 4 results, not 8.
• Exactly one head is not a group.