Question

A three digit number 3a5 is added to another 3-digit number 933 to give a 4-digit number 12b8, which is divisible by 11. Then find the value of a + b ?

Answer 1

Given a + 3 = b (i)
3 a 5
+ 9 3 3
12 b 8
For 12b8 to be divisible by 11
(8 + 2) -(b + 1) = 0 $\Rightarrow$ 10-b-1=0$\Rightarrow$ 9-b=0$\Rightarrow$ b=9
$\therefore$ From (i) a = 6
$\therefore$ a + b = 6 + 9 = 15