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1 answer:
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Social Security numbers are of the form XYZ - MN - ABCD
Part A:
The first three digits XYZ are referred to as the area number
X is a number 1 - 7 (1, 2, 3, 4, 5, 6, 7)
That means we have 7 choices for X
Y and Z can be any number 0 - 9 (0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
That means we have 10 choices for Y and also 10 choices for Z
So, the number of possible ways are
But we know that the area code 666 has never been used.
So we need to subtract this one from the total.
Therefore, the total number of possible area codes is 699.
Answer:
angle BEF = 100 degrees
Step-by-step explanation:
For a regular 9-sided polygon (nonagon),
each exterior angle = 360/9=40 degrees
each interior angle = 180-40 = 140 degrees.
Referring to diagram, in the trapezoid (trapezium) BCDE, the base angles are 180-140 = 40 degrees.
Therefore angle DEB = 40 degrees
that leaves BEF = 140-40 = 100 degrees
