A 3-digit number 4a3 is added to another 3-digit number 984 to give a 4-digit number 13b7, which is divisible by 11. Then, (a + b) = ?

Question: A 3-digit number 4a3 is added to another 3-digit number 984 to give a 4-digit number 13b7, which is divisible by 11. Then, (a + b) = ?

[A].

10

[B].

11

[C].

12

[D].

15

Answer: Option A

Explanation:

4 a 3 |
9 8 4 } ==> a + 8 = b ==> b – a = 8
13 b 7 |

Also, 13 b7 is divisible by 11      (7 + 3) – (b + 1) = (9 – b)

  (9 – b) = 0

  b = 9

(b = 9 and a = 1)     (a + b) = 10.