I have a pyramid, I have height, perimiter, a, b, c (all sides of the base triangle) . I need to calculate the area of each of the side faces, that is the area of the three triangles without the base triangle. I did it. Kind of. I am off by 0.3, but that's possibly due to square roots which is why I am posting this here. I had to use the calculator to solve this because of the square roots. I won't have the calculator with me during exams, so are there any other ways to solve this?