Solve the Sequence Puzzle

What is a sequence puzzle and how can we solve it? Let me give an example of such an sequence puzzle.

Got any clue how to solve this sequence puzzle? The key to solving sequence puzzles is to look at the terms next to each other and guess how they might be related to each other. Let’s name the left hand column the index (numbers) and the right hand side the (sequence) terms.

2 -> 6
3 -> 12
4 -> 20

Let’s first try to find the sequence term for 6 at index 2.  Let’s add these neighboring indices to come to the answer: 2+3 = 5.  This should have been 6. So adding indices did not work.

So let’s try to multiply the neighboring indices for index 2.

2:      2*3 = 6

This seems right. Let’s try this for the indices 3 and 4 also.

3:     3*4 = 12
4:     4*5 = 20

Bingo. We found the solution.  In other words if my multiply the current sequence index with the next sequence index we find the correct term of this sequence.

Now let’s compute the final missing term. We got index 9. The next index is 10. So multiplying these indices 9*10 = 90.  Ninety is the correct answer.

For more fun with solving puzzles check out my last post about math puzzles: Climb the Pyramid.