alvin

if the key to Q2 is 10,the answer is wrong,
if the number can be divided by 15,the last digit should be 0 or 5,if it requested the max,5 is required in the last digit,the the whole number can be divided by 15,it should also be divided by 3,(2+4+2+a+b)/3=...which means (13+a)/5=...and the condition given is a,b are less tham 7,thus,the max number for a in this problem should be 5,thus a=5,b=5,the max ab=25

niubi69

是是是,我是太粗心.你说的对.