First, because the side length ratio is 15: 10 = 3: 2, one side length of the big square is divided into 3: 2 after diagonal connection, that is, the upper part is divided into15× 3/5 = 9 cm; The lower part is15× 2/5 = 6 cm; The area of a is 9×15÷ 2 = 67.5cm ㎡; The area of B is: 6×10 ÷ 2 = 30cm 2; Then a is greater than b: 67.5-30 = 37.5cm2. ..

The second a and b are similar triangles.

Let the right-angled side of A be xcm and the right-angled side of B be ycm.

Available: x+y= 15, x/y= 15/ 10.

Solution: x=9, y=6.

Therefore: S A -S B =37.5cm2.