147 cm as all square based .height = 20 cm m. height= ids ( The diag A tetrahedron has edges of 20 cm as shown. 20 cm 20 cm 20 cm 2 ed triangle, edge 2 m. of edge 40 B A 20 cm M 10 cm 10 cm C (a) Draw ABC and calculate BM. (b) What is the area of ∆ABC? (c) What is the length of VM? B (d) Draw AVMB and measure and calculate MN. (c) What is the area of ∆VMB? (0) If h is the height of ∆VMB, write down the area of ∆VMB in two different ways and so calculate the volume of the tetrahedron. 13.3 The surface area of a pyramid *You have investigated pyramids in​