What is the sum of all three-digit numbers which leave a remainder 3 when divided by 5?
All numbers that fall under this category can be described as 5n+3, where n is a number.
The smallest 3 digit number that fits in the expression 5n+3 is 103. The greatest is 998. The list of these numbers is 103, 108, 111, ...998. The number of numbers in this list is (998-103)/5+1=895/5+1=179+1=180.