Transcript X = {2, 3, 4, 5, 6, 7, 8, 9} Y = {0, 1} Z = {0, 1, 2, 3, 4, 5,

X = {2, 3, 4, 5, 6, 7, 8, 9}
Y = {0, 1}
Z = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
Before 1990, telephone area codes in the United States were three-digit numbers of
the form xyz. Shown above are sets X, Y, and Z from which the digits x, y, and z,
respectively, were chosen. How many possible area codes were there?
(a)
919
(b)
160
(c)
144
(d)
126
(e)
20
Correct Answer: B
Explanation:
There are 8 possible digits for the first digit, x, of the area code, 2 possible digits for
y, and 10 possible digits for z. Therefore, the number of possible area codes would
be 8 x 2 x 10 = 160. The correct answer is B.