SOLUTION: Use either the fundamental counting principle or the permutation formulas (or both) to answer the following How many seven-digit phone numbers can be formed if the first digit c

Question 148725: Use either the fundamental counting principle or the permutation formulas (or both) to answer the following
How many seven-digit phone numbers can be formed if the first digit cannot be 0 and
repetition of digits is not permitted?
if repetition of digits is permitted?
The Board of Directors does not have assigned

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Use either the fundamental counting principle or the permutation formulas (or both) to answer the following
How many seven-digit phone numbers can be formed if the first digit cannot be 0
and
repetition of digits is not permitted?
Ans:
1st digit: 9 ways
2nd digit: 9 ways
3rd to 7th digits: 8!/2! = 8*7*6*5*4*3 = 20160
Total 9^2*20160 = 1632960
--------------------------
if repetition of digits is permitted?
Ans: 9*10^6 = 9 million
--------------------------
Cheers,
Stan H.
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