The first volume of mathematics exercises in the fifth grade of Beijing Normal University Edition is 20CM long and 10CM wide. Fold an isosceles triangle, open and tear a corner, what is the remaining area? The first volume of mathematics exercises in the fifth grade of Beijing Normal University Edition is 20CM long and 10CM wide. Fold an isosceles triangle, open and tear a corner, what is the remaining area?

Fold a rectangular paper with a length of 20CM and a width of 10CM into an isosceles triangle. The essence of a rectangle is the area of two triangles. Open the tear corner and tear off half an isosceles triangle. The remaining area is the area of the rectangle minus half of the isosceles triangle.

20* 10/2= 100 cm2

100/2=50 cm2

20* 10-50= 150 cm2