ABSTRACT
It is possible to find, by drawing, the area of an irregular shape. The technique does not give an exact answer but, carefully used, can provide a reasonable answer. Look at Fig. 17.1 . The shape is trapezoidal with irregular end lines. A centre line has been drawn and you can see that the shaded triangles at the top and bottom are, in their pairs, approximately the same in area. Thus, the approximate area of the whole figure is the width W multiplied by the height at the centre. That height is called the ‘ mid-ordinate ’ and the whole technique is called the ‘ mid-ordinate rule ’ .
