By putting the equilateral triangles with 1cm one side in order without any gap nor overlap, a big equilateral triangle is made.
(1) How many equilateral triangles with 1cm one side are used for the equilateral triangle with 4cm one side?
(2) The equilateral triangle of 1cm, 2cm, 3cm, 4cm ---- one side is named as the 1st, the 2nd, the 3rd, the 4th, ----- equilateral triangle, respectively.
Answer the following questions.
① How many equilateral triangles with 1cm one side are used for the 26th equilateral triangle?
② I made two equilateral triangles, one is a certain numerative number and another is the following.
There are in total 1013 pieces of equilateral triangles with 1cm one side are used for the two equilateral triangles.
Find the numerative number of each equilateral triangle.