Here is a tough mathematical puzzle only for the genius.
This question apparently appeared in UPSC Final Exams held in December 2013 and only 1 person was actually able to solve it.
So the difficulty of this riddle is considered to be “Very Hard”.
 +  +  = 30
Fill the boxes using one of these numbers 1, 3, 5, 7, 9, 11, 13, 15
You can also repeat the numbers.
If you get the correct answer, share it with your friends on WhatsApp, Facebook and other social networking sites.
This is a tough riddle to crack.
The main issue here is that an addition of odd numbers for odd times will result in an odd number. So in no way will you get an even number like 30 by adding these odd numbers.
So you will have to think out of the box to solve this one.
Use of mathematical operator is a must.
To get an even number from an odd number the best operation to use would be factorial.
So we use 3!, (3 factorial)
3! = 3 x 2 x 1 = 6
Now you can fill the 3 boxes with the following;
3! + 15 + 9 = 30