Dia answered question 5/6/2010 What Is The Area Of A Triangle With A Base Of 18m And A Height Of 20m? Area of triangle = 1/2 (base * height) here base is 18m and height is 20m so just put these values in the above formula area of triangle= 1/2 ( 18m*20m) area of triangle = 1/2 (360m^2) area of triangle =180m^2