Three digits can't possibly add up to 900. The largest possible sum of 3 digits is (9 + 9 + 9) = 27.
900 of them.
There are 900 6-digit palindromes.
Assuming that 001, 080, etc are not allowed (that is a leading zero or two is not permitted), the smallest number with exactly three digits is 100. The largest number with exactly three digits is 999. So there are 999 - 100 + 1 = 900 numbers with exactly three digits.
There are nine numbers which contain only one digit. There are 90 numbers which contain two digits. There are 900 numbers which contain three digits. There is one number which contains four digits.Therefore, the number of digits is equal to (9x1)+(90x2)+(900x3)+4 = 2893 digits. If this includes spaces, there would be 999 spaces, therefore there would be 3892 keystrokes.
3 of them.
Yes
890
900
300, 600 and 900.
Three digits can't possibly add up to 900. The largest possible sum of 3 digits is (9 + 9 + 9) = 27.
850
450 or 900
144, 324, 576, 900
900 of them.
There are 900 6-digit palindromes.
There are 900 three-digit numbers.