Question

1.) Is 81 a multiple of 3? Explain how you know

Answer 1

Yes.a multiple of 3=add the numbers so 8 plus 1 is 9 and divide that by 3 it works
2.no.fthe number formed by its last two digits is divisible by 4, the original number is as well. 
3.no.take the last digit, double it, and subtract it from the rest of the number. 
4.yes.Add the digits. If that sum is divisible by nine, then the original number is as well.
5.no . has to work with both
Multiple of 2 --> is even (ends with 0, 2, 4, 6 or 8) 
Multiple of 3 --> digits add up to a multiple of 3.