If you mean *equilateral* triangles, the area of one triangle is 625 √3 cm^(2). That's about 1080 cm^(2), which is about 0.108 m^(2). This gives around 185 triangles, which is frustratingly between options C and D.

I suspect this problem came along with a picture that gave an additional clue about the triangle, like whether it's the legs or the base that is 50 cm, or what one of the angles is; and you didn't give that clue in your data.