A tent is a pyramid standing on a square base of side 6 $m$, and each of its four sloping faces is a triangle of slant height 5 $m$. Find the area of canvas in the four sloping faces, in $m^2$.

Each sloping face is a triangle on a 6 m base with height 5 m measured up the slope: ½ × $6\times 5=15{\text{m}}^2$. Four of them give $60{\text{m}}^2$. (Dropping the ½ gives $120{\text{m}}^2$; the tent's vertical height is √$(5^2-3^2)=4$ m, and using that in place of the slant height gives $48{\text{m}}^2$; adding the $36{\text{m}}^2$ of ground gives $96{\text{m}}^2$, but a tent needs no canvas on the floor.)