Question 1 Given Set A {-1, 0, 1} & set B {-2, 1, 2}, how many combinations are there when A + B > 0?

-- Answer -- 5/9

Numerator -> Write out all of the combinations where the statement is true: (-1+2), (0+1), (0+2), (1,1), (1,2)

Denominator -> How many combinations are there 3*3 = 9

Probability A + B > 0 = 5/9

Question 2 4 balls are in a jar with numbers 1-4. What's the probability the sum will be 5 if 2 balls are chosen?

-- Answer -- 1/3

Numerator => 1,4 & 2,3 & 4,1 & 3,2 … 4 combinations

Denominator -> 4 * 3 * 2 * 1 = 12 combinations

Probability = 4/12 = 1/3

Question 3 Given set a = {-1, 0, 1}, b = {-2, -1, 0, 1}, what is the probability ab > 0?

-- Answer -- 5/12

ab > 0 when (-)(-) or (+)(+) ,

(-)(-) -> numerator = 2 (-1*-2 and (-1*-1), denominator = 12 combinations (3 numbers in set A & 4 in set B)

(+)(+) -> numerator = 1 (1*1), denominator = 12 combinations (3 numbers in set A & 4 in set B)

(-)(-) + (+)(+) = 2/12 + 1/12 = 5/12