3. 232 and 111 are both three-digit palindromes as they read the same from left to right as they do right to left. What is the sum of the digits of the largest three-digit palindrome that is also a multiple of 6 ?
A 16
B 18
C 20
D 21
E 24
SolUtion
E

For a number to be a multiple of 6 , it must be even. Therefore to make the number as big as possible it must start with 8 to also end in 8 . Then it must also be a multiple of 3 , so its digit sum is also a multiple of 3 . This leaves 828,858 and the largest possibility, which is 888 . This has a digit sum of $8+8+8$, which is 24 .