A math problem in a textbook This is the fourth and eighth exercise of the sixth grade of pep Children's weight should not exceed 3 / 20 of their weight. If they carry heavy objects for a long time, it will cause low back pain and backache, and even hinder bone growth Wang Ming: weight 30kg, 5kg in the schoolbag (1) Is Wang Ming's schoolbag overweight? Why? (2) Weigh your weight and figure out how many kilograms you'd better not carry. (I can't do this.) my weight is 35kg

A math problem in a textbook This is the fourth and eighth exercise of the sixth grade of pep Children's weight should not exceed 3 / 20 of their weight. If they carry heavy objects for a long time, it will cause low back pain and backache, and even hinder bone growth Wang Ming: weight 30kg, 5kg in the schoolbag (1) Is Wang Ming's schoolbag overweight? Why? (2) Weigh your weight and figure out how many kilograms you'd better not carry. (I can't do this.) my weight is 35kg

If you carry heavy objects for a long time, it will lead to low back pain and backache, and even hinder bone growth. Wang Ming: 5kg (1) is Wang Ming's schoolbag overweight? Why

1) In an oral examination, three questions should be randomly selected from ten questions to answer. If you answer two questions correctly, you will pass. A candidate will answer six questions in ten questions. What is the probability of his or her passing?
2) There are three volumes in a set of books: upper, middle and lower. If they are listed on the same shelf, what is the probability that the list will be in the order of upper, middle and lower from left to right or from right to left?

(1) There are C (10.3) kinds of questions randomly selected from the 10 questions, and there are two kinds of situations when the examinee passes the exam, two kinds of situations when the examinee answers the two questions correctly, two kinds of situations when the examinee answers the two questions correctly, two kinds of situations when the examinee answers the two questions correctly, two kinds of situations when the examinee answers the two questions, two kinds of situations when the examinee will draw the two questions, and one kind of situations when the examinee does not draw the one kind of situations when the examinee answers the two questions correctly, so the examinee answers the two kinds of situations, namely, C (6.2) * C

A math problem in the textbook, solve it
There is a high-speed wind belt at an altitude of 10km above the earth's surface. Suppose there are two planes with the same speed flying in this wind belt. One of them flies from a to B at a distance of 4000km, which takes 6.5 hours. At the same time, the other takes only 5.2 hours to fly from B to A. what is the average speed of the plane and the wind? (accurate to 1km / h)?

Let the speed of the plane be V1 and the wind speed be v2
There are
6.5（V1 － V2）＝ 4000
5.2(V1 + V2)＝4000
The solution is as follows
V1 = 651km / h
V2 = 118 km / h

1. A cylindrical container with a bottom diameter of 20 cm contains some water. When a conical lead block with a height of 10 cm and a bottom diameter of 12 cm is immersed in water, how much will the water surface drop when the lead block is removed
We need a complete formula,

V (cone) = π R ^ 2H / 3 = (3.14 * 6 * 6 * 10) / 3 = 376.8 cubic centimeter
The bottom area of the cylinder is π R ^ 2 = 3.14 * 10 * 10 = 314 square centimeters
So the height of the drop is 376.8 / 314 = 1.2 cm

The relationship between light energy, electric energy and heat energy
Is there any relationship among the three~

Light energy, such as solar energy, can be converted into electricity and heat
Electricity can be converted into light energy such as lighting and heat energy such as electric blankets
Heat energy can be converted into electrical energy, such as thermal power generation and light energy
In short, the three can be transformed into each other

On factorization?
（1） 198²—396X202+202² （2）202²+202X196+98²
Then there is the known a + B = 2, then what is the value of a & # 178; - B & # 178; + 4B? Thank you very much

(1) Original formula = 198 & # 178; - 2 × 198 × 202 + 202 & # 178;
=（198-202）²=16
(2) The original formula = (202 + 98) & #178;
=90000
(3) From a + B = 2: a = 2-B, substitute a = 2-B into a & # 178; - B & # 178; + 4B
Original formula = 4 + B & # 178; - 4b-b & # 178; + 4B = 4
You are not familiar with this type of question, so I recommend a learning website. You can search the questions of junior high school and its solution ideas and process. Then, it's a coincidence that the name of this website is "detailed solution process" written on your question, and the two words "detailed and process" are deleted

How many grams is 100 Jin?

50000

When a = - 2, - a2-2a + 1=______ When 2A + 3B = 1, 8-4a-6b=______ ．

When a = - 2, - a2-2a + 1 = - 4 + 4 + 1 = 1, when 2A + 3B = 1, 8-4a-6b = 8-2 (2a + 3b) = 8-2 = 6

Two incandescent bulbs with the same rated voltage and different rated power are connected in series. Under their rated voltage, will the one with higher rated power be on? Why?)
If the rating is large, it must be bright, and the reason must be found.

According to P = u & sup2; / R, the same rated voltage indicates that the resistance of the bulb with high rated power is small. According to P = I & sup2; R, the greater the resistance is, the greater the actual power is, so the bulb with high rated power must be bright

It is known that the quadratic equation with real coefficients x ^ 2 + (m-2) x + 5-m = 0 has two different real roots, and both of them are greater than 2

Discriminant △ = (m-2) ^ 2-4 (5-m) > 0
M ^ 2-16 > 0
M > 4 or M4 (x1-2) (x2-2) > 0
So 2-m > 4 leads to M0 and M > - 5
So after synthesis, it is - 5