Question

If 713512A1 is divisible by 3, find all possible values of the missing digit A

Answer 1

The sum of digits of a number divisible by 3 is a multiple of 3
3+5+a+6+4=3n
18+a=3n
If n=6⇒18+a=18⇒a=0
If n=7,⇒18+a=21⇒a=3
If n=8⇒18+a=24⇒a=6
a=0,3,6