Question 705839
Let the unit digit be u then 
u = 0,1,2,3,4,5,6,7,8,9


Let the tens digit be d, the tens digit is twice the units digit
then 2u=0,2,4,6,8,10,12,14,16,18
so d=2u must be a digit so d=0,2,4,6,8


so number is 00, 21, 42, 62 or 84

technically 00 is not a two digit number so exclude that from answer