Question

What number makes 3 and 71 divisible by 9?

Answer 1

3 only 
7 only 
1 only 
1, 4, and 7 
do you mean which digit is added to 371 so that it is divisible by 3 
test for 3, sum of digits divisible by 3 
3 + 7 + 1 = 11 
if you add 3, 11 + 3 = 14 not divisible by 3 
if you add 7, 11+ 7 = 18 divisible by 3 
if you add 1, 11+ 1 = 12 divisible by 3 
if you add 1, 4, 7 divisible by 3