Here’s an interesting mind twister:

A chocolate costs 1 rupee each. You can also exchange 3 wrappers for a chocolate. If you have 15 rs, how many chocolates can you get??

I posted the question on my facebook wall and instantly started getting lots of answers from friends. To my surprise many of them got it wrong. I even had to explain the logic to some of them before they could understand why the answer was *22*.

**Logic:**

You can exchange the 15 wrappers for 5 chocolates. Now you have 15 chocolates without wrappers and 5 with wrappers.

Now exchange three more wrappers for a chocolate. Now you have 18 chocolates without wrappers and 2+1 chocolates with wrappers.

Again exchange the 3 wrappers for one more chocolate. Now you have 21+1=22 chocolates.

Here’s an interesting variation of the problem.

**You can buy 5 chocolates for rs.4 but only one with re.1 . You have 50 bucks in your pocket.As before, you can exchange 3 wrappers for a chocolate. What is the max number of chocolates you can have and the number of wrappers you will have in the end ??**

*Here’s the logic leading up to the correct answer*

12 bucks 22 chocolate + 1wrapper

36 bucks 67 chocolate + 1wrapper

48 bucks 89 chocolate + 2wrapper

49 bucks 91 chocolate + 1wrapper

50 bucks 92 chocolate + 2wrapper

In fact, the question can be used as a programming problem. Here’s the source code in php. Even if you don’t know php, the logic is clear enough for anyone to understand.

` <?php`

$chocolate = 0;

$wrapper = 0;

$money = 50;

```
``` $chocolate = 5*(int)($money/4);

$chocolate += $money%4;

$wrapper = $chocolate;

echo $chocolate;

echo $wrapper;

while($wrapper>=3)

{

$temp = (int)($wrapper/3);

$wrapper = $temp + (int)($wrapper%3);

$chocolate += $temp;

echo $chocolate;

echo $wrapper;

` }`

?>