Monday, May 19, 2008

Are You Smarter Than a 7th Grader

More from my son's homework. What is the missing number and why:

2 2 2 2
2 6 10 14
2 10 26 50
2 14 50 ?


At 11:38 AM, Anonymous Bismuth said...

Here's a hint: it's a variation on Pascal's Triangle

The numerical answer is equal to the square root of 15876.

I'll check back tomorrow with a full explanation as to why.

At 11:54 AM, Blogger wysiwyg said...


Thanks Bis, I understand why now that I know the trick, but REALLY, year 7 math?

I think high school math is looming to be rather more of a challenge than I was anticipating.

At 4:05 PM, Blogger wysiwyg said...

I also sent this around work, and a LARGE number of people figured it out. Which serves to make me feel thicker than ever.

BUT, someone suggested it was 110 based as follows:

1st sequence is T(n) = 2

2nd sequence is T(n) = 2 + (n-1) * 4

3rd sequence is T(n) = 2 + ((n-1)!) * 8

4th sequence is T(n) = 2 + ((n-1)**2) * 12

At 11:41 PM, Anonymous Bismuth said...

Yeah, it's not so much math as it is pattern recognition.

For anyone who is still clueless, each number is the sum of three numbers:

a)the number immediately above it
b)the number immediately to the left of it
c)the number diagonally adjacent, above and to the left

or to visualize it


where X is the number and a, b, and c correspond to a) b) and c) above.

At 2:26 AM, Blogger Trillian said...


At 4:51 AM, Blogger Sarah O. said...

Oy. This is why I stopped helping the kids with math when they were in 5th Grade.

At 9:16 AM, Anonymous Anonymous said...




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