## we are going to discuss some of the puzzles, challenges or brain teaser which are viral in social media such as Face book ,whats app and twitter    etc. which are based on Mathematics directly or indirectly . You have seen such types of puzzles mentioned 99.9% Fail , Solve if you are genius like this........ Let us try to discuss and solve them.  PUZZLE # 1 Which number should replace the ?

4 ,  9 ,  19  ,  39  , 79   ?

## Even Number

When any Number is divisible by  2 then that number is called An Even number. If we take 2, 16, 84, 22, 20, 100 etc then they are Even Numbers as they can be divided by 2.

Let us learn Multiplication , division , arithmetic and simplification short cut ,tips and  tricks after buying this Book of Magical Mathematics.

## Odd Number

When any number is NOT divisible by  2 then that number is called An ODD number .If we take 21, 15, 49, 21, 57, 101 etc then they are Odd  Numbers as they can NOT  be divided by 2.

## Multiple of 3

An number which is divisible by 3 or which comes in the  table of 3 is called  multiple of 3. if we take 57, 102, 69, 9, 6, 21, 39 etc numbers , as these numbers comes in the table of 3 or these are divisible by 3 , so they are Multiple of 3.

## Prime Number

Any number which has only two Factors 1 and the numbers itself is called Prime number. 1 is not the the prime number, 2 ( It is the 1st prime number ) , 3, 5, 7, 11, 13, 17, 19, 23  etc  are examples of Prime numbers as these numbers have only two factors 1 and the number itself.

## Square Number

Any number whose square root is a Natural  number is called square Number . such as  1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144 etc.

## Factors of 360

All those numbers which can divide 360 are called factors of 360 .Here We can take such numbers as 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 18, 36 etc

## Analyse the Answers above  , we get  4, 6, 8, 10, 12, 14, 16, 18 and 20. Is there any relation between them. Of course, Because every answer is 2 more than the previous Answer. So Last number  should be 200. so in order to get answer 200 we have to multiply  20 with 10. So       If 2  =  8                  3  = 18                 4  = 32                5  = 50                 6  = 72                  7  = 84                8  = 128                9  = 172                10 = 200  Then    10 = 200 In order to get any number any of any term  based upon this trends we can use the formula  2n² , where "n "  is the number appearing on left side of the Puzzle.

So Final Answer will be 200

Here is the Solution of the Puzzle asked in "HOW TO SOLVE HARD AND IMPOSSIBLE PUZZLES PART 3" as follows.

There are two numbers 'a' and 'b' in 1st and 2nd columns then 3rd column has been  occupied by their combination as follows

a*b = (a2  + b2 ) - 1,

1*3 = (12  + 32 ) - 1 = ( 1 +   9) -1  = 10 - 1 =  9

3*4 = (32  + 42 ) - 1 = ( 9 + 16) -1  = 25 - 1 = 24
2*5 = (22  + 52 ) - 1 = ( 4 + 25) -1  = 29 - 1 = 28
4*5 = (42  + 52 ) - 1 = (16 + 25) -1 = 41 - 1 = 40

So 40 will replace  ?  in this puzzle

## Thanks for devoting your valuable time for this post  "How   to solve various Hard and impossible puzzles ,Quizzes ,  Brain Teasers and challenges " of my blog . If you liked this this blog/post,  Do Follow me on my blog and share this post with your friends . We shall meet again   in next post with solutions of most interesting and mind blowing puzzles ,till then Good Bye.