Question

Please help!
The telephone Number of a district has this format: NYZ ABC-XXX,
where NYZ is area code.
a. How many all possible area codes are there if N is 6-9, Y is 3-
8 and Z is 0-9 in this district?
b. The 7-digit numbers in the district have the form ABC-XXXX,
where X, B, and C can be any digit 1–9 and A is restricted to
3–8. How many 7-digit numbers there?
c. How many possible telephone numbers in the district?

Answer 1

n,y,z
n can be 5, y can be 6, z is 10

Answer 2

are you aware of tree diagrams

Answer 3

isnt n 4? @518nad

Answer 4

yes, there are 4 possible values of n.
Choices of n, y and z are independent, so the multiplication rule applies.
In fact, the multiplication rule applies to the other questions as well, i.e. multiply together the number of possible choices for each digit, since the choice of each digit is independent of the other digits.

Answer 5

oh yes oops