Lateral area is always equal, because no matter what you do, lateral area is the area of this paper.

Namely: 18.84 * 12.56 (square centimeter)

Of course, you can take it like this:12.56 *18.84 (cm 2) hehe .. What's the difference? It's really no different. ..

Let's look at the folding method again. There are only two kinds, either the length of a rectangle is the height of a cylinder or the width of a rectangle is the height of a cylinder:

The first folding mode (cylinder height = 18.84 CM),

Of course, the width is the circumference of the upper and lower circles. According to the circumference formula of a circle, C = 2πR r r.

Then we get:12.56 = 2π r r.

At this time, R:R = 12.56/2π can be found.

Then calculate the area of the circle at this time, according to the area formula of the circle: s = π * r 2 = π * (12.56/2π) 2.

Then the volume of the cylinder can be calculated: v1= s * h = π * (12.56/2 π) 2 *18.84.

The same algorithm can also get the volume of a cylinder with the width of a rectangle as the height of the cylinder.

v2 = s * h =π*( 18.84/2π)^2 * 12.56

Then compare V 1, V2. How come?

Do it yourself It's time to exercise yourself. )

Start running CALC and switch to scientific calculation mode.

2. The second problem is that there is a closed cylinder toilet. Why the toilet? Don't ask me, then Xiaoming threw a stone in. You can put a piece of incense in it if you like. Oh, it's a bad boy.

This is actually a test of common sense, because the liquid is flowing and the water is squeezed after the stone is thrown in. At this time, in this certain space, the volume of the rising water surface is equal to the volume of the stone. Then you know what to do.

Since they are equal, it is better to calculate the volume of this water, because the toilet is a cylinder.

We only need to know the circular area of the cylindrical toilet.

Because the circumference is 15.7 CM. According to the old rule, C = 2πR r r.

So we know what r equals.

R = 2π/C, substitute the value given in the title.

Then find the area.

S = π * R^2 is substituted into the r calculated in the previous test.

Finally, calculate the volume of water,

V = S * H

Just substitute it into the calculation. They are all known quantities.

In fact, this question is about physical knowledge. There are a few things to understand, 1. The container for throwing stones is a cylinder. This cylinder is closed. The rest is not a problem. My purpose is to guide you to think, do specific calculations, or do it yourself. This calculation can deepen your understanding.