Bend a 20 cm long wire into a rectangle and a square. Guess who has the largest area,

Bend a 20 cm long wire into a rectangle and a square. Guess who has the largest area,

…… Of course, square, make an equation to verify, very simple, square area must be 25, rectangular area is a * (20-a), you just need to prove that the rectangular area is always less than 25, two minus one minus, with the complete square formula below, the result will come out~

With a 40 cm long, 20 cm wide rectangular sheet iron, four corners cut 5 cm long square, make a rectangular iron box, volume and surface area
What is the difference

40-5 × 2 = 30 cm
20-5 × 2 = 10 cm
Volume: 30 × 10 × 5 = 1500 cc = 1500 ml
Surface area: 40 × 20 - 5 × 5 × 4 = 700 square centimeter

The area of the shadow part in the square accounts for 1 / 6 of the area of the circle and 1 / 5 of the area of the square; the area of the shadow part in the triangle accounts for 1 / 8 of the area of the circle,
1 / 9 of the triangle area. Find the simplest integer ratio of square, circle and triangle area

Circle area: square area = 6:5; circle area: triangle area = 8:9. The least common multiple of 6 and 8 is 24, so it is 20:24:27

A circle is divided into four parts vertically and horizontally along the center of the circle. There is also the largest square in the circle. The area of the known triangle is 10 cm. Calculate the shadow area
There is a circle, which is divided into four parts along the center of the circle. In the circle, there is the largest square in his body. This square is composed of four triangles. It is known that the area of the triangle is 10 square centimeters. How much is the area of three fourths of the circle?

The area of a triangle is 10
He is an isosceles right triangle, and the two right sides are equal to the radius of the circle R,
So triangle area = 1 / 2 * r * r = 10, and R * r = 20 square centimeters
Circle area = π * r * r = π * 20 = 20 π square centimeter
Its 3 / 4 area = 3 / 4 * 20 π = 15 π square centimeter