As shown in the figure, put a circular shear with a radius of 10cm into an approximate rectangle, and the perimeter of the current rectangle is () cm A. 31.4B. 62.8C. 72.8    D、82.8

As shown in the figure, put a circular shear with a radius of 10cm into an approximate rectangle, and the perimeter of the current rectangle is () cm A. 31.4B. 62.8C. 72.8    D、82.8

3.14 × 2 × 10 + 10 × 2, = 62.8 + 20, = 82.8 (CM); answer: the circumference of this rectangle is 82.8 cm

The perimeter of a rectangle is 100cm. When the length of the rectangle decreases by 10cm and the width increases by 10cm, the rectangle just becomes square
Question: how many centimeters are the length and width of the original rectangle

Length: width: length: 20cm width (100 / 2-20) / 2 = 15cm length: 15 + 20 = 35cm ~ if you agree with my answer, please click the [adopt as satisfied answer] button in time ~ ~ the mobile phone questioner can click [satisfied] in the upper right corner of the client. ~ your adoption is my driving force ~ ~ if there are any new questions, please don't send them in the form of follow-up questions

A square and a circle, perimeter is 6.28dm, square area is (), circle area is ()

Square side length = 6.28 △ 4 = 1.57 decimeters
Area = 1.57 × 1.57 = 2.4649 square decimeters
Radius of circle = 6.28 △ 3.14 △ 2 = 1 decimeter
Area = 1 × 1 × 3.14 = 314 square decimeters