Use the expression for the area of a trapezoid, which is equal to 1/2 [ sum of the parallel sides x distance between them ]
1(b) A cutting is to be made through rough ground. The width of the bottom has to be a constant 4m and the sides of the cutting must be at a slope of 1 in 1. The depth s of the cutting at 6 m intervals are :-
(a) 1.8m (b) 1.4m (c) 1.4m (d) 1.8m (e) 2.0m (f) 2.6m
(g) 3.2m (h) 3.6m (i) 2.8m (j) 2.6m (k) 2.4m (l) 2.8m
(ii) Determine the cross sectional area for each cross section.
The cross section is an isosceles trapezoid.
The area of a trapezoid is: .Code:: - h - : - - 4 - - : - h - : * * * * * * * * * * * * * * * * | | * * |h | * * | | * 45o * * * * * * * - - - : - - 4 - - :
. . where is the height, and are the lengths of the two bases.
We have height and bases and
Now plug in the thirteen values for