It seems a very straight forward question.
Question
You have 80 apples. You divide them by half and add another 30 apples . How many apples you are left with ??
Hint : It is not 70 !!!
Answer
At the first glance , we make calculation that
We have 80
Dividing it by half , half of 80 is 40
Then add 30, totally 70 apples !!!
But it is clearly said answer is not 70.
We will again go through question.
It says, we have 80 apples.
Divide them by half !!!
Here is the culprit.....
We must divide by half, not dividing by 2 !!!
That means, 80 / ( 1/2 )
==>> 80 * 2 = 160 !!!
Now again add 30 apples.
==>> 160 + 30 = 190 Apples.
Finally we are left with 190 apples !!!