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PROBABILITY & COMPLEMENTS #3--KEY

Directions:  The complement of an event can be looked at as the opposite of that event, or everything besides that event.  The probability of an event and the complement of that event will always add up to a total of 1.  For the problems below, find the probability of each event described and the probability of its complement.

Example:  Flipping a coin 10 times and landing on tails 7 times.    P (tails) = 7/10		P( heads) = 3/10	        		

1)  Flipping a coin 20 times and landing on heads 11 times.		P(heads) = 11/20                     P(tails) = 9/20

2)  It snowed three days last week.		                                     P(snow) = 3/7              P(no snow) = 4/7

3)  A jar with 15 marbles, 7 are red.		                                      P(red) = 7/15                 P(not red) = 8/15

4)  Rolling a 1 on a regular die.		                                      P(one) = 1/6                 P(not one) = 5/6

6)  You had homework in 2 out of 7 classes.		                          P(H-work) = 2/7           P(no h-work) = 5/7

7)  Flipping a coin 35 times and landing on tails 19 times.		  P(tails) = 19/35                  P(heads) = 16/35

8)  Your ten digit phone number has one 3 in it.		              P(three) = 1/10             P(not three) = 9/10

9)  A jar with 2 red, 3 green, and 5 blue marbles.		              P(green) = 3/10                     P(not) = 7/10

10)  Rolling a number less than 5 on a regular die.	                     P(<5) = 4/6 or 2/3                    P(>5) = 2/6 or 1/3

11)  Flipping a coin and getting 7 tail and 4 heads.	                          P(tails) = 7/11              P(not tails) = 3/11

12)  Picking an ace out of a regular deck of 52 cards               P(ace) = 4/52 or 1/13     P(not ace) = 48/52 or 12/13

13)  A jar with 13 marbles, 2 are red, 6 green, the rest blue.	             P(blue) = 5/13             P(not blue) = 8/13