Funny in germany we learn the formular for just that:
Area_triangle = Base_triangle * Height_triangle / 2
/edit: fixed factor of two
Area_triangle = Base_triangle * Height_triangle / 2
/edit: fixed factor of two
(You are of by a factor of 2)
Try to draw a triangle such as the one mentioned.
When PISA came out in 2000, Finland was surprised to come out on top for Europe. Germany's performance in math was abysmal -- behind the US even. People started flocking to see what Finland did, and stopped looking up to Germany.
https://nces.ed.gov/pubs2002/2002116.pdf
The German school system has since gradually improved -- it's no longer behind the US -- but it's far from world-leading.