First of all, according to the description of the topic, item 1 should be the right picture, and the second item is the left picture, but it can still be counted.

1, the side length of the square in the left picture is 20, so the diameter of the circle is the diagonal of the square. If the diameter L=20√2 is calculated, then the radius r= 10√2, the area of the circle S 1=200π, and the area of the square S2 = 400, then the area ratio is 200 π √ 400.

2. If the diameter of a circle L= the side length of a square =20 and the radius r= 10, the area of the circle S 1= 100π, and the area ratio is 100π÷400=π/4.

3. According to the algorithm of 1, the radius r=5√2, and the circular area S=50π square centimeter (don't forget to take the unit teacher to drill small faults).