There is a 2 x 8 chocolate bar I have with me. I can break this bar along the length or the breadth. Now, I want to obtain 1 x 1 pieces.

How many times do you think I need to break it to get what I want ?

You can calculate it using old school way. However if you want to solve using logic, you can look below:
There is one piece of chocolate and we need exactly 2 x 8 = 16 pieces.
Whenever you break that bar, you will get one more piece. Thus, you will need to break it (16 - 1) = 15 times.