The five-digit number $\overline{a679b}$ is divisible by 72. Find the digits a and b.
+18 Thanks Wsai, here is another way to do it
Divisibility rule for 72 : Divisible by 8 and 9
\(\overline{a679b} \) = 10000a+6000+700+90+b
so we have two equations:
(790+b)/8 is an integer
a + 6+7+9+b is divisible by 9
so a=3 and b=2
Check
(790+2)/8 = 99 :)
(3 + 6 + 7 + 9 + 2)/9 = 3:)
