You have 6 stick lenghths 10,20,30,40,50 and 60cm find the number of noncongruent triangles that can be formed using three sticks as sides
The key here is that for a triangle with sides of length a, b, and c we know that the sum of the length of any two sides is longer than the length of the third side. That is:
a + b > c
a + c > b
b + c > a