18
There are 6804 such numbers.
27: 077,177,277,377,477,577,677,877,977,717,727,737,747,757,767,777,787,797
well, i think if you use this you can find out. A = 1-9 ,B = 0-9 , C = 0-9 , D = 0-9 , E = 0-9 for 2digit numbers = A A for 3 digit numbers = A B A for 4 digit numbers = A B B A and so on till you get to for 8 digit numbers = A B C D D C B A for 9 digit numbers = A B C D E D C B A and last for 10 digit number = A B C D E E D C B A this should work...
18
There are 22680 numbers, excluding those with leading 0s.
17
There are 9000 4-digit numbers. 8*9*9*9 = 5832 of them do not contain a 5 The remaining 3168 contain a 5.
-2
-5
-5
It would help to know which digit. 0 appears in 9 numbers and each of the others in 18 numbers.
252
There are 6804 such numbers.
The pages of a book are numbered from 1 to 128. How many page numbers contain the digit 6?
648
874
252