A math solution, very fast, fast

Cylindrical timber low area: 20 2 = 10 square decimeters.

Cylindrical timber area 10 1 10 = 100 square decimeters.

From the inscription, the surface area has increased by 20 square meters, and the area of the round bottom is 10 square meters, and the area of the original wood is.

10*10+10+10=120 square decimeters.

Hope it helps.

If the surface area is increased by 20 square decimeters, then the bottom area is 10 square decimeters.

Radius r = (10), length 1 m = 10 dm.

It turns out that the area of this wood = 10 + 10 + 10 * 2 r = 20 + 20 (10).

1 meter = 10 decimeters.

The surface area has increased by 20 square decimeters, indicating that the base area is 10 square decimeters, and the cylinder = base area * height = 10 * 10 = 100 cubic decimeters. Hope.

I guess it's 20+10 times the base girth.

The base circumference is equal to x

The equation about x is: multiplied by the square of the radius of the base surface is equal to 10

Multiplying by 2 times the base radius is equal to x (base circumference).

The answer is not a score.

Solution: The area of the bottom of the cylinder is.

20dm²÷2=10dm²

The total area is 10x2+10x【(10)】 lookout.

1 meter = 10 decimeters Two bottom areas have been added, 20 * 2 = 10 (square decimeters) 10 * 10 = 100 (square decimeters) area to be changed to volume!

Base area = 20 2 = 10 square decimeters Volume = 10 10 = 100 cubic decimeters.

liters = cubic decimeters = 38,400 cubic centimeters.

38400 (50 24) = 32 centimeters.

The water surface is 40-32 = 8 cm from the upper mouth.

Volume = length times width times height = 50 24 40 = 48000cm liters = 38400cm

38400÷（50×24）=32cm

40-32=8cm

A: - Can it help you?

Profit and loss issues. Formula: (P&L + P&L) Difference between two distributions = number of units (here is the time required).

8*50+5*60) (60-50)=70 (points).

Distance: 2*50+(70+8)*50=4900 (meters).

Walking 50 meters in 2 minutes, that is, the speed is 25 meters, and the distance from home to school is x meters, x 25-8 = (x-50) 60 + 2 + 5

Suppose it takes him t minutes to get from home to school.

50*(t+8)=50*2+60*(t-2-5)50t+400=100+60t-420

t = 72 homes and the distance to the school is 50 * (72 + 8) = 4000 meters.

There are still x minutes of lessons.

2+x+8)50=2*50+(x-5)60

Solve the number of x and bring in (2+x+8)50 to calculate.

If the temperature inside the classroom is 10°C on a given day and the temperature outside the classroom is -3°C, the temperature difference between the inside and outside of the classroom is 13

Observations show that the first figure has 1 triangle, the second has 4, the third has 9, and the fourth has 16 ,..They are 1 2, 2 2, 3 2, 4 2....Therefore, n has n 2 triangles.

Solution: (2) There are [n] triangles of the same size as the painted triangle in the nth figure;

3) There is a matchstick in the fourth figure;

4) There is a matchstick in the tenth figure.