Q18 of 64 Page 122

In a certain city, all telephone numbers have six digits, the first two digits always being 41 or 42 or 46 or 62 or 64. How many telephone numbers have all si x digits distinct?

Given:- all telephone numbers have si x digits


the first two digits always being 41 or 42 or 46 or 62 or 64.


=5


First two digits should can be fill in 5 ways


The four-digit remaining will be filled in


=8P4


Therefore, telephone numbers have all six digits distinct


=5×1680


=8400


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