so a little riddle

[sunnyirish08]

fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-prn1/154226_375242109225729_359382210_n.jpg


found this on facebook, i personally disagree with the two answers given. i thought this might prove a distraction for those who need to be distracted.

[biochemgeek]

Well, I found 21, and I'm not sure that's all of them.

ETA: Make that 23

[sunnyirish08]

yup, found 23 as well.

[sunnyirish08]

in my typical fashion, my bro who's a maths prof in the states. sent me this on facebook

That's a really nice problem: I think it's 16+7+3+1 = 27. It would be nice to figure out if you replaced the big triangle of side length four with a big triangle of side length five, or more, and see what pops out.

[katlyn520]

Oct 27, 2012 0:58:31 GMT -5 sunnyirish08 said:

in my typical fashion, my bro who's a maths prof in the states. sent me this on facebook

That's a really nice problem: I think it's 16+7+3+1 = 27. It would be nice to figure out if you replaced the big triangle of side length four with a big triangle of side length five, or more, and see what pops out.

I got 27 as well. Using your brother's equation, there are 16 single triangles, 7 that include four small triangles (one is upside down, 3 that include nine small triangles, and the 1 large triangle.