Today is another sunny day. I was wandering in the street when I suddenly saw a lot of people gathered not far away. I ran for a year, and the result was a prize-winning game. "Hum, what's fun about winning the prize?" I was bored when the person next to me quickly said, "It's not fun to grab the prize, but there is a big prize that can attract people." I asked eagerly, "What is it!" "50 yuan money." The man with big eyes said. I'm very excited to hear that. "I have to try anything for such an attractive prize." Then I asked the shopkeeper how to grasp the rules. The shopkeeper said, "This is 24 Mahjong, and it says 12 5, 12 10. You can only catch 12 mahjong at a time. If the total number of 12 mahjong targets is 60, then you can win the 50 yuan Prize. " Without rolling up my sleeves, I took out 5 yuan money from my pocket and gave it to the shopkeeper.

Although I won 10 times, I still didn't win the grand prize.

When I got home, I thought about it and felt something was wrong. I think, to get 60 points, all 12 mahjong should be marked with 5. In the best case, the first 1 second catch 1 5, the second catch of two 5 s and the third catch of three 5 s will cost at least 6 yuan money. But what if the target number of mahjong is 10 or the sum of the two is the same, how many times will it cost?

Finally, after some consideration, I finally figured it out. I rushed to the street to look for an account, but I ran away without a trace.

Saturday, February 28th is fine.

When I read the newspaper today, I saw such a topic: Find the surface area of a cone.

[Title] A cone, the diameter of the bottom surface is 6 meters, and the length from the apex of the cone to any point on the circumference of the bottom surface is 5 meters. Find the surface area of this cone.

Although I have never learned to calculate the surface area of a cone, I have learned the surface area of a cylinder. By solving the surface area of cylinder, I know that the surface area of cylinder is equal to one side plus two bottom areas, while the surface area of cone is one lateral area plus one bottom area, and the side is a sector. Although I haven't studied it, I have checked the data and know that the area of a sector is: the area of a sector = arc length × circle radius × 1/2. The topic has told us that the length from the apex of the cone to any point on the circumference of the bottom surface is 5m, while the arc length is 3. 14×6= 18.84 (m), and the sector area is18.84× 5×1/2 = 47./kloc.

Mathematics is the gymnastics of thinking. As long as we study hard and think hard, we will certainly overcome the problems and embark on the road to success!

Tuesday, 2 March

Every time I go to Tomb-Sweeping Day, there will be a sea of people on the giant mountain, so some swindlers come up with some deceptive tricks, such as gambling on something on a plate.

Prop is very simple, draw a big circle on a board, and fix a rotatable pointer in the center of the big circle with a nail. The great circle is divided into 24 equal squares, and the needles in the squares can rotate. The box says 1-24 equal numbers, which are worthless in the odd box, but almost all even numbers are valuable.

The gameplay is also very simple. Set the pointer to 1 first, then you dial the pointer again, and the pointer will start to rotate and finally stop in a grid. Then press the number marked on the grid where the pointer is located and dial the pointer again. N- 1 grid, where n is the number marked on the grid.

This is just a little math game. In fact, no matter which box you dial, you can only lose money, not make money. Because when the pointer turns to an odd cell, the number of cells dialed is odd-1= even, and odd+even is only equal to odd, so it is impossible to turn to an even cell and nothing valuable can be obtained. If the pointer turns to an even grid and the number of grids dialed is even-1= odd, and odd+even = odd, then you won't get anything of value.

Friday May 12

Calculate wages

At noon, my father came back from work, humming a ditty, and happily stepped into the house. I greeted him and asked, "Dad, what's so happy today?" Dad said, "I got a raise this month." I asked, "How much salary do you get now?" Dad thought for a moment, smiled and said, "My salary is higher than your mother's. Our monthly salary adds up to 2800, and the monthly salary difference is 100. How much do you think I get a month? "

After listening to my father's words, I began to draw line drawings on paper to help me understand:

Through observation and thinking, I quickly worked out the answer and told my father. First of all, mom's salary is as much as dad's, so mom and dad's monthly salary is (2800+ 100)=2900 yuan, and then the total monthly salary is divided into two parts, and 1 part is dad's monthly salary. The formula is: (2800+ 100)÷2= 1450 yuan.

Dad listened and nodded with satisfaction. At this time, my mother, who was cooking, said to me, "Do you have any other methods?" "Is there any other way?" I said in surprise. I stopped to observe and think curiously. I found that the key to this problem is to find out who is the standard. Different standards have different methods. So, I have a second method: taking mom's salary as the standard, assuming mom and dad's salary is the same, then the sum of their monthly salary is (2800- 100)=2700 yuan, and then divide the sum of monthly salary into two parts on average. 1 part is mom's monthly salary, and finally it is more than mom's 100. The formula is (2800-100) ÷ 2+100 =1450 yuan.

After listening to the second method I introduced, mom and dad both laughed. ...

It will be sunny on Wednesday March 24th.

The electric fan factory plans to produce 1600 electric fans within 20 days. After five days of production, due to the improvement of technology, the work efficiency has increased by 25%. How many days will it take to complete this task?

Analysis: This problem can be solved by direct proportion method through transformation. If the original efficiency is "1", then the actual efficiency is (1+25%)=5/4, and the ratio of actual efficiency to original efficiency is 5/4: 1 = 5: 4, because efficiency is inversely proportional to time.

It will take x days to complete this plan.

4∶5 = X∶20-5

5X=4× 15

X= 12

A: It takes 12 days to complete the plan.

Saturday, March 27th is fine.

I was bored today, so I took out a math newspaper, and suddenly a very special topic attracted me.

[Title] There is a rectangular iron sheet, which can be made into a cylinder by cutting off the shadow in the picture. The radius of the bottom of this cylinder is 2 decimeters, so what is the area of the original rectangular iron sheet?

[Analysis and Problem Solving] Look carefully at the right. The width of the shadow rectangle can't be the circumference of the bottom of the cylinder, so the circumference of the bottom of the cylinder is the length of the shadow rectangle. In addition, we can also find the width of the rectangular iron sheet, that is, the height of the cylinder is twice the diameter of the cylinder bottom, and the diameter of the cylinder bottom+the perimeter of the cylinder bottom is equal to the length of the rectangular iron sheet. Therefore, the length of rectangular iron sheet is 2× 2+2× 3.14× 2 =16.56 (decimeter) and the width is 2×2×2=8 (decimeter). The area of the original rectangular iron sheet is 16.56×8= 132.48 (decimeter).

Saturday, March 27th is fine.

Think about problems in combination with reality.

Think about it, where is he wrong?

[Title] There are two cylindrical wooden columns in a hall. The diameter of the bottom of the wooden column is 0.6m, and the height of the column is 6m. If you want to paint their surface, how many square meters is the painted part?

After reading this question, Xiao Qiang felt very simple. He quickly listed the formula and worked out how many square meters the paint area was.

3.14× (0.6÷ 2 )× (0.6÷ 2)+3.14× 0.6× 6× 2 = 23.7384 (square meter). A careful analysis of the meaning of the problem reveals that Xiao Qiang's idea is completely wrong, and the reason for the mistake is that he didn't think about the problem in combination with reality. Although the wooden column is cylindrical, as far as practical problems are concerned, the painted part does not include the upper bottom surface and the lower bottom surface. Therefore, it is necessary to draw part of the area to find the side area of these two cylindrical wooden columns. The formula should be: 3. 14×0.6×6×2=22.608 (square meter). A: The area of the painted part is 22.608 square meters.

I have written down your serial number, and I will make it for you when it is adopted.