Bob the builder has many sticks of length 3, 5, and 7. He wants to form triangles whose edges consist of exactly 1 stick. How many non-congruent triangles can he form with the sticks?

Answer 1

Heck, the only set of sides which cannot work is

3,3,7

So, list all those with all 3 sides the same,
those with two sides the same
those with all different sides.

Answer 2

I don't get what you mean?

Answer 3

Examine the unique triplets of numbers that can be created with 3,5, and 7. There are 10 of them. Any other triplet of numbers would be a rotation or reflection of these. 3−3−33−3−53−3−73−5−53−5−73−7−75−5−55−5−75−7−77−7−7 You might think that the answer is 10, but remember that in a triangle, the sum of the lengths of any two sides must be greater than the length of the third side. This eliminates 3−3−7 as a possible triangle, so the answer is 9

The correct answer is: 9