Choose (put the serial number of the correct answer in brackets) A bag of rice has 64 kg, if you eat 3 kg a day, enough to eat () days A.20 B.21 C.22

Choose (put the serial number of the correct answer in brackets) A bag of rice has 64 kg, if you eat 3 kg a day, enough to eat () days A.20 B.21 C.22

A bag of rice has 64 kg, if you eat 3 kg a day, enough to eat (b) days
64÷3=21…… one

Choose the serial number of the correct answer and fill in the brackets
1. If 7a = 8b (A and B are not equal to 0), then a ∶ B = ((a) 1 ∶ 1 (b) 7 ∶ 8 (c) 8 ∶ 7) 2. The product of the product of two prime numbers must be ((a) composite number 3. The following (a, B, (b) prime numbers) (c) odd (d) even number) 4. A cone and a cylinder have the same volume and the same bottom area, Then the ratio of the height of the cone to the cylinder is () (b) 1 ∶ 3 (c) 3 ∶ 1 (d). It is impossible to judge whether (a) 1 ∶ 1 is broken. 5. In the following figures, there are only four symmetrical axes ((a) square (b) rectangle) (d) circle (c) equilateral triangle. 6. A number on a two digit ten is a, and a number on a single digit is B. this two digit number can be expressed as ((a) AB) (b) a + B （C）10ab （D）10a+b

1. If 7a = 8b (A and B are not equal to 0), then a ∶ B = (c) (a) 1 ∶ 1 (b) 7 ∶ 8 (c) 8 ∶ 7) 2. The product of the product of two prime numbers must be (a) (a) composite number B, (b) prime number) (c) odd number (d) even number) 4. The volume of a cone is equal to that of a cylinder, and the area of its base is also equal

Choose (put the serial number of the correct answer in brackets)
The volume of a cylinder is ()
1. Cylinder 2, cuboid 3, the same size

It's as big as three
Volume of cylinder = base area * height
Cuboid volume = base area * height

The basic steps of solving linear equation with one variable

General solution: 1. To the denominator: on both sides of the equation multiplied by the least common multiple of each denominator (do not include the denominator of the term should also be multiplied); 2. To brackets: first to small brackets, then to brackets, and finally to braces; (remember that if there is a minus sign outside the brackets, you must change the sign) 3

A (x ^ my ^ 4) / (3x ^ 2Y ^ n) ^ 2 = 4x ^ 2Y ^ 2. Find the value of a.m.n

a(x^my^4)/(3x^2y^n)^2
=a(x^my^4)/(9x^4y^2n)
=(a/9)*x^(m-4)*y^(4-2n)
=4x^2y^2
So a / 9 = 4, M-4 = 2, 4-2n = 2
So a = 36, M = 6, n = 1

Please use calculus to deduce the volume formula of positive cone

Let's talk about the derivation process Just like the derivation of the area of a circle, two methods can be used: one is to divide the frustum laterally into pieces, and each piece is integrated according to the cylinder; the other is to cut the frustum longitudinally from the center of the circle, and each piece is integrated according to the ladder

Definite integral formula
What are∫ sec DX and ∫ CSC DX equal to? Is there anything else except ∫ secx DX = ln [secx + TaNx] + C ∫ CSCX DX = ln [CSCX Cotx] + C?

∫secx dx=(1/2) ln|(1+sinx)/(1-sinx)| +C
∫cscx dx=(1/2) ln|(1-sinx)/(1+sinx)| +C
But it's equivalent to the two you said

How is the area formula of trapezoid derived?
It is helpful for the responder to give an accurate answer

(top bottom + bottom bottom) x height divided by 2

Who can introduce Liu Hui, an ancient Chinese mathematician?

Liu Hui (about 225-295 A.D.), Han nationality, born in Linzi, Shandong Province, was a great mathematician during the Wei and Jin Dynasties and one of the founders of Chinese classical mathematical theory. He was a very great mathematician in the history of Chinese mathematics. His masterpieces "notes on arithmetic in nine chapters" and "Suanjing on islands" are the most precious mathematical heritage in China

The area formula of circle is derived from trapezoidal area formula
How to deduce the area of a circle with trapezoidal area formula? I know the area formula of a circle, and I need to know how to deduce it
Note that the formula is pushed down

The area formula derivation of circle
The circle is divided into even number of sectors, and each two sectors are combined into an approximate rectangle. All these sectors form an approximate large rectangle. The length is half of the circumference of the circle, and the width is the radius. When the division tends to infinity, the approximate rectangle is the rectangle. According to this, the area of the circle can be calculated
(a rectangle can be regarded as a trapezoid)