A cuboid container, with a bottom area of 16 square decimeters and a water height of 6 decimeters, is now put into an iron block with a volume of 24 cubic decimeters? 2. The stadium is paved with 37.5 coal cinders on a 100 meter long and 7.5 meter wide straight track. How many centimeters thick can the cinders be paved? 3. A rectangular timber with a square cross section has a surface area of 118 square centimeters. After sawing off the largest cube, the surface area is 54 square centimeters. What is the surface area of the sawn cube timber?

1. The volume of water is 16 * 6 = 96 cubic decimeter;
After adding iron, the water surface will rise. At this time, the whole volume should be the original volume of water plus the volume of iron, that is: 96 + 24 = 120 cubic decimeters;
Now the volume is calculated, divided by the bottom area of the container is the height of the water surface: 120 / 16 = 7.5 decimeters
2. The road paved with cinder is actually a cuboid, the bottom area is the area of runway, and the height is the thickness of cinder
Bottom area = 100 * 7.5 = 750;
The thickness of coal seam is: 37.5 / 750 = 0.05m = 5cm
3. Because the bottom of the wood is square, the largest cube sawed off is the cube of a section of wood, and the side length is the side length of the square on the bottom. Set the side length as x cm;
If you saw off a cube, the surface area of the whole wood will be reduced by 4 squares with x cm sides (you can easily see it by drawing a picture on the paper), that is 4x ^ 2;
So the formula is 4x ^ 2 = 118-54
The solution is x = 4
The surface area of the saw cube is the sum of six squares with side length of x cm, that is, 6 * x ^ 2 = 6 * 4 ^ 2 = 96 square cm

Cuboid container, the bottom area is 16 square decimeters, the height of water is 6 decimeters, put a 24 cubic decimeter iron block, the iron block will be completely submerged, how many decimeters of water surface rise at this time? (water does not overflow)

Water volume + iron volume = 16 * 6 + 24 = 120 (cubic decimeter)
So the water surface height: 120 △ 16 = 7.5 (decimeter)
Namely: (16 * 6 + 24) △ 16 = 7.5 (decimeter)

The bottom area of a cuboid container is 16 square decimeters, and the water height is 6 decimeters. Put an iron block with a volume of 24 cubic decimeters to make it sink into the water completely. What is the water height at this time?

Water volume + iron volume = 16 * 6 + 24 = 120 (cubic decimeter)
So the water surface height: 120 △ 16 = 7.5 (decimeter)
Namely: (16 * 6 + 24) △ 16 = 7.5 (decimeter)

The speed of the bus and the truck is 4:5. How many kilometers does the truck travel per hour

900/5=180
Bus: 180 * 4 / (4 + 5) = 80 km / h
Truck: 180 * 5 / 9 = 100 km / h

Log2 (2x-1) is less than log2 (one x plus 5)

Log2 (x) increases monotonically at (0, + infinity),
So if you want the above formula to hold, you just need to satisfy it
0

A and B each walk for a certain distance. Their speed ratio is 3:4 and the time ratio is 4:5. What is the distance ratio of a and B,

Let a speed 3a, B speed 4a, a time 4T, B time 5T
The distance a takes is 3A * 4T = 12At, and the distance b takes is 4A * 5T = 20at
So the distance ratio is 12At: 20at = 3:5

With unknowns______ It's an equation

An equation with unknowns is an equation, so the answer is: an equation

Spacecraft is powered by the reaction of air, but outer space is a vacuum environment. How can spacecraft get power?

It's not the reaction force of air, but the reaction force from the ejected gas. It's similar to the recoil force of the gun when a bullet is fired out of the muzzle. The principle is that momentum is conserved. Air produces only resistance to the rocket, so after the rocket flies out of the atmosphere, its speed will be faster, but its mass will be smaller and smaller, f = MV, so the total mass of the rocket fuel

The solution of the equation is the value of the unknown

It's not right
The solution of the equation is x = The value of the unknown is only a numerical value. They are different concepts

Two identical tubes are filled with different liquids of equal mass. Tube a is placed vertically and tube B is placed obliquely. At this time, the liquid level in the two tubes is at the same horizontal position. Which tube is under the pressure of the liquid?
But how do you know which one is denser?

The higher the density, the higher the pressure
The vertical pressure is high, because the inclined pipe is longer than the vertical one. Put the bottom ends of the two pipes together and draw a line on the liquid surface to form a right triangle. The right side is shorter than the inclined side, so the volume is smaller and the density is higher