Question 1160041: ow many 7-digit telephone numbers are possible if the first digit cannot be six and
(a) only even digits may be used?
(b) the number must be a multiple of 10 (that is, it must end in 0)?
(c) the number must be a multiple of 1 comma 000?
(d) the first 3 digits are 192?
(e) no repetitions are allowed?
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! a. Even digits are 2,4,6,8,0.
4 ways to choose the first*5^6=62,500
b. then there are 10^6 or 1 million.
c. then there are 10^4 or 10,000
d. then there are also 10^4 or 10,000
e. 10*9*8*7*6*5*4=604,800
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