It is known that one side of the cuboid without box cover is square, and the length of the two edges is 4cm and 5cm respectively. The surface area and volume of the box are calculated

It is known that one side of the cuboid without box cover is square, and the length of the two edges is 4cm and 5cm respectively. The surface area and volume of the box are calculated

It can be considered in two cases: 1. Suppose that the side length of a square is 4cm. (4 * 4 + 4 * 5 + 4 * 5) * 2 = 112cm2 Surface area 4 * 4 * 5 = 80 cm3 Volume 2. Assume that the side length of the square is 5 cm. (5 * 4 + 5 * 4 + 5 * 5) * 2 = 130 square cm Surface area 4 * 5 *

It was originally planned to take Liping three hours to get from home to the county by bike. Due to the uneven road of 5.6 kilometers on the way, this section of the road is equivalent to 3 / 4 of the original speed, so she arrived late
How long is it from Liping's home to the county in 12 minutes

If the desired speed is x km, then the original speed is x / 3 km / h
5.6/[(x/3)*(3/4)]-5.6/(x/3)=12/60
The solution is x = 28 km

Research paper on "my mathematics and life" in Grade 6

The wire with length of 1 is divided into two sections and enclosed into a square and a circle respectively. In order to minimize the sum of the area of the square and the circle, the perimeter of the square should be___ ．

Analysis: let the perimeter of the square be x, then the perimeter of the circle is 1-x, the radius r = 1-x2 π. S positive = (x4) 2 = x216, s circle = π · (1-x) 24 π 2. S positive + s circle = (π + 4) x2-8x + 416 π (0 < x < 1). When x = 4 π + 4, there is a minimum value. Answer: 4 π + 4

Given the square of a = y-ay-1, the square of B = 2y-ay-2y-1, and the value of polynomial 2a-b has nothing to do with the letter Y, find the value of a!

a=y^2-ay-1 b=2y^2-ay-2y-1
2a-b=2(y^2-ay-1)-(2y^2-ay-2y-1)
=2Y^2-2ay-2-2y^2+ay+2y+1
=-ay+2y-1
=(2-a)y-1
Since the value of 2a-b is independent of the letter Y, 2-A = 0, that is, a = 2

After 3 weeks, 2 880 were found. After 5 weeks, 5 120 were found
1 seek growth ratio R
2. Original number of insects
Write a growth formula of insects
I know to use e ^ x to make a formula and calculate... But I can't remember

Let the equation be y = am ^ x, 2880 after 3 weeks, 5120 2880 after 5 weeks = am ^ 3, 5120 = am ^ 5, M = 4 / 3, a = 1215
The equation is y = 1215 (4 / 3) ^ x, the growth ratio = 4 / 3, and the growth formula is y = 1215 (4 / 3) ^ X

If the side length of a square is increased by 3 cm, its area is reduced by 45 square cm. Find the original side length of the square. If the side length is decreased by 3 cm, its area is reduced by 45 square cm, find the original side length
Square~

The increased area of Tzq is the yellow and pink part in the figure, that is, two rectangles and a square. The side length of the square is 5cm, and the length of the rectangle is the side length of the original square, and the width is 5cm
95-5 * 5 = 70cm2, i.e. two rectangular areas (yellow part)
70 / 2 = 35cm2, that is, the area of a rectangle
35 / 5 = 7cm, that is, the length of the rectangle is the area dcd95 of the original rectangle

It is known that it takes 8 minutes and 20 seconds for sunlight to reach the earth from the sun. The earth's orbit can be approximately regarded as a fixed orbit, and the earth's radius is about 6.4 * 10 ^ 6m
The ratio of positive mass m to earth mass m?

The distance between the sun and the earth is r = [(8 × 60) + 20] × 3 × 10 (8th power) = 500 × 3 × 10 (8th power) s = 1.5 × 10 (11th power)
The sun is the central celestial body with a mass of:
GMm/ R²=m4π²R/T²
M=4π²R³/GT²
Assuming that the acceleration of gravity on the earth's surface is g, the mass of the earth can be calculated
GM’m/r²=mg
M’= r²g/G
M / M '= 4 π & # 178; R & # 179; R & # 178; T & # 178; G (where R is the distance between the earth and the daytime, R is the earth's radius, t is the earth's revolution period, and G is the acceleration of gravity on the earth's surface)

The concept of stress and strain

The concept of stress is similar to that of pressure, which refers to the magnitude of the force per unit area. The unit is the same as that of pressure: PA, kPa, MPa, etc, Results when the wire is extended by 1 mm, the strain is 1 mm / 1 m = 0.001

The perimeter C (CM) of a square is known, and its area is s (CM & # 178;) (1) find the functional relationship between S and C; (2) draw the image of s with respect to C; and;
(3) According to the image, calculate the perimeter of the square when s = 1cm & # 178; (4) according to the image, calculate the sum value of C when s ≥ 4cm & # 178;

c=4r;s=r*r;=>s=c*c/16;
When s = 1, C = 4;