A big rectangle in math problem consists of four areas: 12 cm2, 36 cm2, 24 cm2 and 48 cm2.

Solution: The area of the upper two blocks is 12 36=48 square centimeters.

The area of the lower two blocks is 24 48 = 72 square centimeters.

The greatest common divisor of 48 and 72 is 24,

Therefore, the area of 12 square centimeter is 2 centimeters high and 6 centimeters long at the bottom.

The area is 36 square centimeters, the height is 2 centimeters, and the bottom length is 18 centimeters.

It covers an area of 24 square centimeters, 3 centimeters high and 8 centimeters long at the bottom.

The area is 48 square centimeters, the height is 3 centimeters, and the bottom length is 16 centimeters.

The base length of the shaded part is 18- 16 = 2cm.

2× 2 ÷ 2× 3 ÷ 2 = 5 square centimeters.

The shadow area is 5 square centimeters.

So the answer is: 5.

Hope to adopt, thank you.

Hey, upstairs, do you need to copy my answer to the question of intellectuals to please the landlord?