A four-digit number can be made by repeating a two-digit number. For example, 1111 is made by repeating 11, and 1919 is made by repeating 19 . How many such numbers are there between 2000 and 10000 ?
(A) 80
(B) 81
(C) 79
(D) 72
(E) 70
Each four-digit number must be greater than 2000, and so the smallest two-digit number that may be repeated is 20 (to give 2020).

Each four-digit number must be less than 10000 , and so the largest two-digit number that may be repeated is 99 (to give 9999).

Each two-digit number between 20 and 99 may be repeated to give a four-digit number between 2000 and 10000 .

In total, there are $99-20+1=80$ numbers that satisfy the given conditions.

ANswer: (A)