How to calculate the sum of the equation What is the equation? How many do you get?

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3) Let the radius be x, 2x+ x=, and the solution is: x=2cm; Area=2 2* 2=;

4) Let the diameter of the circle be x, x 2+x= and the solution is: x=12 cm; Area = (12 2) * 2 = cm2;

5) (1): 2*2*3+2*2**3 3= distance from the center of the circle, 2*2* *3 3 3 120 degree sector arc length);

2) 4*2*2+2*2**4 4= distance from the center of the circle, 2*2*4 90-degree sector arc length).

3) Let the cross-sectional radius of the log be x,5x - =, and obtain: x=; (5 * 2 = this question is actually a regular problem, from the above two questions can be seen, in fact, the total length of the center distance of the front circle is the radius of the two circles and 4, a few circles are multiplied by a few, the circumference of the arc behind has nothing to do with the number of circles, the total length is fixed as the circumference of a circle).

3: Set to x, 2x*, x=2 Area = 2*2*4: Set to x, x=12 Area = (12 2) *5: (1): 2*3+2*2* distance from the center of the circle, 2*2*3 120 degree sector arc length).

2) 4*2+2*2* the distance of the center of the circle, 2*2*4 90-degree fan arc length) 3) the first 2 turns, for the circumference of a circle).

0, yuan. 0,8x0,5 0,4 yuan for two, how much is 0,11,51 yuan.

Question 6, 1 [(50 100) (40 100)]=1 (, the total area of 5 blocks is 1 square meter.

Question 7, 1) 250 40 = 10000 (square decimeter), 10000 100 = 100 (square meter), area 10000 square decimeter, that is, 100 square meters.

2) 100-2 3 = 100-6 = 94 (square meters), the remaining area is 94 square meters.

Question 8, 200 (80 60 100) = 200 48 = 9600 (yuan), 9600 yuan.

Question 9, 1) (8-2) (14-2) = 6 12 = 72 (square meters), green area 72 square meters,

1 hexagonal pentagonal pentagonal quadrilateral: 45 3=151 bananas: (23-15) 2=4

1 banana: 4 4 = 1

1 clock at 3 o'clock: (10-4) 2=3

1 clock at 2 o'clock: 3-1=2

1 hexagonal set pentagon: 15-4=11

Result: 2+(1 3)+(1 3) 11=38

Question 5, circumference = 100 4 + 40 4 = 560 (decimeters), area = 100 40 2 + 40 40 = 9600 (decimeters), question 7, 20 decimeters = 2 meters, 35 2 + 25 2 + 2 2 = 124 (square meters), the area increases by 124 square meters.

Question 8, 40 cm = 4 decimeters, 4 4-1 1 4 = 12 (square decimeters), the remaining area is 12 square decimeters.

Question 9, 5 5 500 100 = 125 (square meters), area 125 square meters.