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Devious Kinder Blocks (Posted on 2008-06-18) Difficulty: 3 of 5
For integral unit increments of x, what equation generates the values of y which are represented in the blocks?

Avoid the obvious.

3
10
21
36


Hint:
The trick works with Internet Explorer, Firefox and Opera but Opera may behave a little differently to mouse explorations; oh, concentrate on the higher part of each block.

See The Solution Submitted by brianjn    
Rating: 4.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Solution where's the trick? | Comment 2 of 8 |

The sequence here is the triangle numbers, although you can only see alternating  ones (the evens) in the diagram without the trick. If you point your mouse at the upperleftmost red part of each letter and hold it there, you'll see a hover effect/tooltip with the missing numbers of the sequence. (If your browser doesn't support this feature, you can also view the html source for the page and find these "tricky" numbers--they all look like TITLE="#" where # is the number in question.

The visible number in the xth block then, is the (2x)th trianglular number. Since the nth triangular number is given by n(n+1)/2, the xth  block's number should be 2x(2x+1)/2 = x(2x+1), which is consistent with blocks A-D above and the assumption that the block labeled A is block 1, B is block 2, and so on.


  Posted by Paul on 2008-06-18 18:36:23
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