Finding the area by knowing the circumference of a rectangle A rope is 31.4 meters long. Is it a rectangle or a square, or a circle? (please calculate the relevant data) The key is the area of the rectangle. I know everything else. I also know that the circle is big, 3Q

Finding the area by knowing the circumference of a rectangle A rope is 31.4 meters long. Is it a rectangle or a square, or a circle? (please calculate the relevant data) The key is the area of the rectangle. I know everything else. I also know that the circle is big, 3Q

4 / 3.14 / 2 = 5 (m) (radius) 5 * 5 * 3.14 = 78.5 (M2) (area of the circle) 31.4 / 4 = 7.85 (m) (side length of the square) 7.85 * 7.85 = area of the square: (31.4 / 4) ^ 2 = 31.4 ^ 2 / 16 = 61.6225 (M2) (area of the square) 78.5 is greater than 61.6225 of course

Given the perimeter of a rectangle, how to find its area?

According to the relevant conditions, we need to get the length and width from the perimeter, then we can get the area of the rectangle

Draw a largest semicircle and a largest circle in a rectangle. It is known that the circumference of the rectangle is 60 cm. Calculate the area of the blank part

Suppose the radius of the circle is r, then the length and width of the rectangle are 3R and 2R respectively, then 2 × (3R + 2R) = 60, so r = 6 (CM), length = 6 × 3 = 18 (CM), width = 6 × 2 = 12 (CM), blank area: 18 × 12-3.14 × 62-12 × 3.14 × 62 = 216-113.04-56.25 = 216-169.56 = 46.44 (square centimeter). Answer: the area of blank part is 46.44 square centimeter

The length of the rectangle is 30 decimeters. What percentage of the area of the semicircle of the rectangle?

3.14 × (30 ﹣ 2) 2 ﹣ 2 ﹣ [30 ﹣ 2], = 3.14 × 225 ﹣ 2 ﹣ [30 × 15], = 353.25 ﹣ 450, = 78.5%; answer: semicircle area accounts for 78.5% of rectangle area

The perimeter of a rectangle is 60cm. Its length and width are prime numbers. What is its maximum area in square centimeters?

The perimeter is 60cm, so the length widening = 30cm, because it is a rectangular side length, and the side length is prime, that is, when the length is 17 and the width is 13, the area is the largest, and the maximum area is 17 * 13 = 221cm & # 178;
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The area of a trapezoid is 21 or 6 square meters, its height is 2 or 4 meters, its bottom length is 6 or 6 meters, and its top length is several meters

21.6*2/2.4-6.6=11.4

The upper bottom of a trapezoid is 5 / 2 decimeters, the lower bottom is 5 / 4 decimeters, and the area is 21 square decimeters. What is the height of this trapezoid?

21×2÷(2/5+4/5)
=42÷6/5
=42×5/6
=35 (decimeter)

The upper bottom of a trapezoid is two fifths of a decimeter, the lower bottom is four fifths of a decimeter, and the area is 21 square decimeters. What is the height of this trapezoid?

Height = 21 × 2 ^ (2 / 5 + 4 / 5) = 35 decimeters

It is known that the area of the trapezoid in the right figure below is 25 square decimeters. Calculate the area of the shadow part

Trapezoid area = (3 + 7) x height △ 2 = 25
So high = 5
Triangle area = bottom x height △ 2
=3x5÷2
=7.5 (square decimeter)

The area of a trapezoid is 25dm2, the upper bottom is 4.8dm, the lower bottom is 5.2dm, and the height is 4.8dm______ ．

25 × 2 △ 4.8 + 5.2, = 50 △ 10, = 5 (decimeter), answer: the height of trapezoid is 5 decimeter