At 1 P. M. the family resumes their trip, and they reach Helena at 5 P. M. The total distance from the family’s home to Helena i
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Answer:
This system have 9000 different numbers.
Step-by-step explanation:
We know that the internal telephone numbers in the phone system on a campus consists of 4 digits, with the 1st not equal to 0.
We have total 10 digits.
In the first place we have 9 possibilities, because from the conditions of the task in the first place there cannot be 0.
In second, third and fourth place we have 10 possibilities.
Therefore, we get
This system have 9000 different numbers.