What is a leap year? Is 1972 a leap year? Is 1900 a leap year

What is a leap year? Is 1972 a leap year? Is 1900 a leap year

Generally, the Gregorian calendar year is a multiple of 4, which is generally a leap year. The calculation method of a leap year: the number of years in the year of A.D. can be divided by 4, that is, a leap year; the year divided by 100, but not by 400, is an ordinary year; the year divided by 100, but also by 400, is a leap year. For example, 2000 is a leap year, 1900 is not a leap year

What's 20 times 22?

440

Xiaoming and Xiaogang are 28 kilometers apart. They agreed to meet and start at the same time. Xiaoming's speed is 8 kilometers per hour and Xiaogang's speed is 6 kilometers per hour. Xiaoming and Xiaogang are 28 kilometers apart. They agreed to meet and start at the same time. Xiaoming's speed is 8 kilometers per hour and Xiaogang's speed is 6 kilometers per hour, Xiaoming's father found that Xiaoming had nothing with him 30 minutes after Xiaoming started, so he chased Xiaoming at the speed of 10 kilometers per hour. When Xiaoming and Xiaogang met, did his father catch up with Xiaoming? If he wanted to catch up with Xiaoming, at least how fast was it?
(solution of linear equation with one variable)

Let X be the time when Xiao Ming and Xiao Gang meet
8x+6x=28
x=2
Dad's journey is 15 kilometers in an hour and a half,
Xiao Ming ran into Xiao Gang at 16 km, so he couldn't catch up
Dad wants to catch up with Xiao Ming. His distance is at least 16 km in an hour and a half, so his speed is at least 16 / 5 km

English translation
1 right now, right now
2 points / lose one point
Do one's best
Be sure to do sth
With the help of sb
6. Confrontation with
7 for a long time
He fell ill in August
Do you mind if I do it?
Don't do it, do you mind
11. Miss a good opportunity
Be ashamed of sb
Feel sorry for sb
With the help of sb
15 serving
Keep sb. Doing sth
17 up / down
18 in a minute, right away
19 on the phone
20 is very important to sb
At 21
It doesn't matter
Enjoy doing sth
24 feel tired
25 follow the rules
26 appears healthy and energetic
27 A 15-year-old boy
Have a great interest in doing sth
29 substitution
Ask sb. To do sth
Make a plan for sb
Enhance, enhance
33 normal operation
34 be with
35 free
36 first time
37 won the first gold medal
39 won 28 gold medals
40 winners
41 every four years, every three years
42 representatives
Enjoy doing sth
A symbol of
What did I say wrong in Building 1? If I say something wrong, just tell me not to do it. I just want to learn more. If I don't want to answer it, I will

At once
To score / lose one point
Try one's best
Be determined to do sth
With the help of sb
Compete with sb
7 a very long time
Fall ill
Would you mind me doing sth?
Would you mind not doing sth?
Miss a good chance / opportunity
Feel shame for sb
Feel / be sorry for sb
With the help of sb
Serve a course
Keep sb. Doing sth sb.doing sth.
17 turn up / down
18 a moment later
19 on the phone
Be important to sb
21 be seated
It doesn't matter
Like to do / doing sth
Feel tired
25 obey the rules
Look healthy and energetic
A 15-year-old boy
Have great interests in doing sth
29 take the place of
Ask sb to do sth
Make a plan for sb
Enhance build up
33 in good order
34 be / stay with sb
Be free
36 the first time
Win the first gold medal
39 won 28 gold medals
The winner
Every four years
42 on behalf of
Like doing / to do sth
A symbol of

When the gardener uses the scissors as shown in the figure to trim the branches, he often puts the branches as close as possible to the scissors axis O, so as to reduce the cost______ It saves effort

In the process of using the scissors in the figure, under the same condition, the scissors are close to the scissors axis O to reduce the resistance arm. From f1l1 = f2l2, it can be seen that the smaller the resistance arm L2, the more labor-saving. Therefore, the purpose of doing this is to reduce the resistance arm, which can save labor

A cuboid is 10 cm long, 8 cm wide and 5 cm high. Cut it into two small cuboids. What is the maximum sum of the surface areas of the two cuboids

The maximum is (10 * 8 + 10 * 5 + 8 * 5) * 2 + 10 * 8 * 2 = 500 square centimeters

Fill in the blanks 0 -- 7-- () -- 18-- () -- () -- () -- () -- () -- ()

13.22.25.27.28.28.27
0+7=7,7+6=13,13+5=18…… and so on

Formula deformation
Under the root sign x square + y square - 1 = under the root sign (X-2) square + y square + 1 (the last + 1 is not in the root sign) how to simplify the square?

Put all the root signs aside, and square both sides of the equal sign. If you put all the root signs aside, there will be no root sign in the square

Regulations for the implementation of the road traffic safety law of the people's Republic of China
The law consists of several chapters and articles

Article 1 These Regulations are formulated in accordance with the provisions of the road traffic safety law of the people's Republic of China (hereinafter referred to as the road traffic safety law)

In 0, 1, 2, 3, 4, 9, 27, 31, 57, 111: how many odd numbers? How many even numbers? How many prime numbers? How many combined numbers?

Odd numbers: 1, 3, 9, 27, 31, 57, 111
Even number: 0,2
Prime numbers: 2,3,31
Total: 4, 9, 27, 57, 111