Question

Find the total number of even 4 digit palindromes

Answer 1

Answer:

2 Answers. There are 90 four-digit palindromes from 1001;1111;1221;1331;... to 9669;9779;9889;9999. Because (12;15;18;21;...;93;96;99) are divisible by 3 and this set has (99−12)÷3+1=30 numbers, there will be 30 palindromes satisfy the task.

Answer 2

There are 90 four-digit palindromes from 1001;1111;1221;1331;... to 9669;9779;9889;9999. Because (12;15;18;21;...;93;96;99) are divisible by 3 and this set has (99−12)÷3+1=30 numbers, there will be 30 palindromes satisfy the task. "⇔" is used to replace "if and only if".