Four identical triangles are cut from a 42 cm by 18 cm rectangle.<br><br>Total area of rectangle = 42 x 18 = 756 cm&sup2;<br>Area of 4 cut-out triangles = 756 minus 672 = 84 cm&sup2;<br>Remaining area = 756 minus 84 = 672 cm&sup2;<br><br>Final Answer: 672 cm&sup2;