There is 90 four digit palindromes.
There are 90 four-digit palindromes
Nine. The sum of the digits must be a multiple of 9; because of the repeated digits, this is only possible if the first two digits add up to 9.
1221, 2112, 3003, 10401, 11211, 12021
The same as the number of two-digit numbers, since the last two digits must the same as the first two, only reversed. So I'll say there are 100 four-digit palindromes.
There is 90 four digit palindromes.
There are 90 four-digit palindromes
There are 90 four-digit palindromes
Nine. The sum of the digits must be a multiple of 9; because of the repeated digits, this is only possible if the first two digits add up to 9.
1221, 2112, 3003, 10401, 11211, 12021
81
The same as the number of two-digit numbers, since the last two digits must the same as the first two, only reversed. So I'll say there are 100 four-digit palindromes.
The same as the number of two-digit numbers, since the last two digits must the same as the first two, only reversed. So I'll say there are 100 four-digit palindromes.
Colorado and wyoming
1024
1024
1600 (square of 40)