30 customers are eating dinner at an Italian restaurant. Of the 30 customers, 60

Question

30 customers are eating dinner at an Italian restaurant. Of the 30 customers, 60% order pizza, 35% order a salad, and 25% order pizza and a salad. 15% customers ordered spaghetti. Using this information, answer each of the following questions:

1. The proportion of customers that ate either pizza or salad.
a)30%   b)40%   c)50%   d)70%

2. The proportion of customers that ate neither pizza or salad. a)30%   b)40%   c)50%   d)70%

3. The proportion of customers that ate something other than pizza, salad, or spaghetti.
a)10%   b)15%    c)20%   d)25%

4. What is the conditional probability that a customer ate pizza given that he or she ate salad?
a)25% b)42%   c)71%   d)85%

5. What is the probability that you choose the correct answer to this question?
a) Not this one.
b) Still not this one.
c) 100%
d) You went too far, go back to c.

Explanation / Answer

1. proportion of customers that ate either pizza or salad is 0.6+0.35-0.25 =0.7 or d)

2. 1-0.7 =0.3 or a)

3. people who ordered either of these meals is 0.7+0.15 =0.85 i.e 15% did not order anything b)

4. P(pizza and salad)/P(salad) =25/35 = 71% or c)

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