Number Olympiad 5 about the area of the third grade

Length + width = 15cm

Length + 4) * (width + 4) = length * width + 4 (length + width) + 16

Then the existing area is 4 (length + width) + 16 = 4 * 15 + 16 = 76 more than the original area

Let the original length be x, then the width is (30-2x) 2 and the area is x times (30-2x) 2

The rear area is (x+4) times [(30-2x) 2 +4].

76 of the subtraction of the two formulas

First of all: x+y=15 The extra area = 4*(y+4)+4*(x+4)-4*4=4*15+4*4=76 So the final answer is 76 where x y is the length and width of the original rectangle It is recommended to draw the following picture to make it easier to understand!!

Let the length and width be each The original area is s, then there is 2(x+y)=30 xy=s (x+4)(y+4)=xy+4(x+y)+16=s+60+16=s+76, so it is increased by 76

Let the length of this rectangle be x, then the width will be (30 2-x).

x+4)(30/2-x+4)-x(30/2-x)=-x^2+15x+76-15x+x^2=76

The second person is right.

I haven't learned equations yet.

The original area of the rectangle is added to 16 square centimeters.

1.A rectangle, if the width remains the same, increases the length by 8 meters, the area increases by 72 square meters, and if the length does not change, the width decreases by 4 meters, the area.

Test center: the area of a rectangle and a square.

Fractional analysis: divide the increased area by the increased length, which is the width of the original number of potatoes, that is, 72 8 = 9 meters; Divide the reduced area by the reduced width, which is the original length, i.e., 48 4 = 12 meters, which can be solved by using the area formula of the rectangle.

Answer: Solution: 72 8 = 9 (m).

48 4 = 12 (m).

12 9=108 (square meters);

A: The area of the rectangle is 108 square meters.

So the answer is: 108 square meters.

Comments: The key to solving this question is: use the area formula of the rectangle to find the original length and width, and the problem can be solved.

Reduced by 48 square meters, the area of the original rectangle is ().

A rectangle, if the width remains the same, the length increases by 8 meters, the area increases by 72 square meters, if the length remains the same, the width decreases by 4 meters, the area decreases by 48 square meters, and the area of the original rectangle is ().

Analysis: divide the increased area by the increased length, which is the original width, i.e. 72 8 = 9 meters; Divide the reduced area by the reduced width, which is the original length, i.e., 48 4 = 12 meters, which can be solved by using the area formula of the rectangle.

Analysis: divide the increased area by the increased length, which is the original width, i.e. 72 8 = 9 meters; Divide the reduced area by the reduced width, which is the original length, that is, 48 4 = 12 meters, which can be solved by using the area formula of the rectangle from Xun Zhao.

Answer: Mu only rent solution: 72 8 = 9 (m).

48 4 = 12 (m).

12 9=108 (square meters);

A: The area of the rectangle is 108 square meters.

So the answer is: 108 square meters.

1.It is 30 meters to use a tape measure to circle around the circumference of the classroom, and the length of the classroom is known to be 8 meters, how many square meters is the area of the classroom?

2.Xiao Ming's father used a 45-meter-long fence against the wall to form a square vegetable patch, how many square meters is the area of this vegetable patch?

3.There is a vegetable plot that is 37 meters long and 25 meters wide. A 1-meter-wide road is left in the middle of the vegetable plot to prepare for the cement bricks, and the vegetable plot is divided into four equal parts, what is the area of each piece?

4.The circumference of a rectangular wheat field is 160 meters, and the length is 3 times the width, how many square meters is the area of this field?

1) A TV screen is a rectangle, its width is 34 cm, 10 cm shorter than its length, what is its circumference?

2) The length of a rectangular vegetable plot is 75 meters, and the width is 3 times, what is the circumference and floor area of this vegetable plot?

3) A square vegetable garden, which is surrounded by a 24-meter-long fence, find the area of this vegetable garden?

4) What is the circumference and area of a rectangular artificial ice rink, which is 25 meters wide and 2 meters less than 2 meters as long as it is wide?

5) The length of a basketball court is 26 meters, which is twice as wide as the width, how many meters is the circumference of this basketball court? How many square meters does it occupy?

6) Zhu Wei ran 3 laps around the square playground for a total of 1200 meters, how many meters is on each side of the playground?

7) A rectangle is 8 cm long and 3 cm wide, how many centimeters must be increased in width to make this rectangle a square? How many square centimeters more square is a square area than this rectangle?

8) There is a rectangular meadow, 14 meters long and 9 meters wide, and now the meadow is to be expanded, the length is increased by 7 meters, and the width is increased by 3 meters, and the area is now many times the original? It turns out that how many meters less than the current length of the meadow is now?

Tell us about the appropriate units to measure the area of stamps, desks, classrooms and playgrounds.

The size of the surface-plane figures of an object, called their area (representing the size of a two-dimensional plane figure), makes it more logical for the definition to truly reveal the essential properties of things, because "face" is a kind of "shape" that "has length, width, but not height". That is, calculate its size, 1, the circumference of the rectangle = (length + width) 2 c=(a+b) 22, the circumference of the square = the side length 4 c=4a

3. The area of the rectangle = length and width s=ab

4. The area of the square = the length of the side The length of the side = a

5. The area of the triangle = the base height 2 s=ah 26, the area of the parallelogram = the base height s=ah

7. The area of the trapezoid = (upper bottom + lower bottom) height 2 s=(a b)h 28, diameter = radius 2 d = 2r radius = diameter 2 r = d 29, the circumference of the circle = pi diameter = pi radius 2 c = d =2 r10, the area of the circle = pi radius radius = r11, the surface area of the cuboid = (length and width + length height width and height) 212, the volume of the cuboid = length and width height v = abh13, The surface area of the cube = edge length Ridge length 6 s = 6a14, the volume of the cube = edge length edge length edge length v= a15, the side area of the cylinder = the circumference of the bottom circle height s=ch16, the surface area of the cylinder = the area of the upper and lower bottom surface + the side area.

s=2πr +2πrh=2π(d÷2) +2π(d÷2)h=2π(c÷2÷π)ch

17. The volume of the cylinder = the bottom area of the height v=sh

v= r h= (d 2) h= (c 2 )h18, volume of the cone = base area height 3

v=sh÷3=πr h÷3=π(d÷2) h÷3=π(c÷2÷π)h÷3

19. The volume of the cuboid (cube, cylinder) = base area height v=sh

For example, if you have four sides of a square, all four sides are equal, and the multiplication of two is its area.

Hello! = 5000 (sqm).

The area is 5000 square meters. Look

The length is exactly 100, and the length is 2 times the width, so the width is 100 2=50, so the area = length and width = 100*50 = 5000

100÷2=50（m²）

100×50=5000（m²）

A: The area of this playground is 5000 square meters.

The formula for the area of a rectangle is length multiplied by height (a b).

Get s=100 50=5000

The area of the rectangle is long times wide, so the length is 100, and the width is half the length, then it is 50, and the area is 5000