Seven-digit telephone numbers are not allowed to begin with 0 or 1
I can only remember a seven-digit telephone number if the first three digits (the "prefix") are equal to the next three digits or the last three digits. For example, I can remember 389-3892 and 274-9274.
How many seven-digit telephone numbers can I remember?
i thought that for the 1st didgit there are 8 choices, the 2nd and 3rd have 10, and then the didgit that doesnt repeat has 10, and then the other ones repeat, and its multiplied by 2 for if the digit that doesnt repeat bieng in front or behind, but im stuck and its wrong apparently.
U can remember infinity numbers If u can which is impossible
Bcz 2 to 9 they are 7 numbers in between even 1st three digits and last 3 digits are same..it is even impossible to remember all numbers they are 7 different numbers in three places of phone and 4th digit is different from everything