I heard that Thailand is a good place for sightseeing

I heard that Thailand is a good place for sightseeing

I heard that Thailand is a good place to go sightseeing

The width of a rectangular iron plate is 30cm, and a small square is subtracted from each of the four corners to make a 5cm high rectangular container. The volume is 300ml (the thickness of the iron sheet is ignored), and how much is the original area of the iron sheet? (I don't understand how to get every data.)

Cuboid volume = length * width * height = 300
Make a cuboid container 5cm high, so the side length of each small square is 5cm
Width = 30-5 * 2 = 20cm
Height = 5cm
The length of cuboid = 300 / (20 * 5) = 3cm
Length of rectangle = 3 + 2 * 5 = 13cm
Area of rectangle = 13 * 30 = 390 square centimeter
There may be some problems in this problem. The cuboid volume of 3000ml is more appropriate

Qianjin primary school divides 360 books into four, five and six grades. One half of the books in the fourth grade are equal to one third of the books in the fifth grade and one fourth of the books in the sixth grade. How many books do four, five and six grades get?

From the meaning of the title, we can see
Fourth grade books: fifth grade books: sixth grade books
=2：3：4
The fourth grade score is 360 × 2 / (2 + 3 + 4) = 80
The fifth grade score is 360 × 3 / (2 + 3 + 4) = 120
Grade 6 got 360 × 4 / (2 + 3 + 4) = 160

1. Which number is different: 2, 3, 6, 11, 15, 21

11 different
1+2=3
1+2+3=6
1+2+3+4=10
1+2+3+4+5=15
1+2+3+4+5+6=21

6、8、12、12、18、16、（ ）、20

24
Note: the rule of item 1357 is that each item is 6 times larger than the previous one
The rule of item 2468 is that each item is larger than the previous one. Divide the original row into two groups

A set of data: 14, 16, 18, 20, 22, 24, 26
A set of data: 14, 16, 18, 20, 22, 24, 26
(1) If we add 2 to each data, how do the range and variance change?
(2) If you multiply each data by 2, how do the range and variance change?
(3) If you divide each data by 2, how do the range and variance change?
(4) Put a set of data x1, X2 Xn, changing to ax1 + B, AX2 + B Axn + B, how do the range and variance change?

(1) (2) range, variance will expand twice. (3) range, variance will shrink to half of the original. (4) take × n + B as an example, range, variance will expand n times, plus a number, the maximum and minimum will increase at the same time, resulting in the range unchanged

-3 4-6 10 group 2 3-5 7-13
There are three ways to do each

(-3)*(-6)+10-4=24
(-6)*10/(-3)+4=24

Observe the number (similar to 24 points)
Observe the numbers of 3, 3, 8 and 8, do not change the order of the numbers, add the operation symbols, and form a formula with these numbers, so that the result is equal to 27

3^3+8-8=27
The third power of 3 Equals 27 + 8-8 equals 0

Each person did at least one right question, including 21 people who did the first question right, 18 people who did the second question right, and 9 people who did both questions right
How many people are there?
Attachment: try to use a way of thinking that is easy for freshmen to understand,

21+18-9=30
Draw two intersecting circles to represent the number of people who are doing right questions 1 and 2 respectively. The intersecting part in the middle represents the number of people who are all right. Fill in the three numbers and it's obvious

Math 7 / 8 = () / 24 = () / 135
7/8=(21)/24=()/135

【OK?】
7/8=(21)/24=(119)/136
7/8=3*7/3*8=17*7/17*8