If it is a pencil drawing, its characteristics are: high softness, elasticity, obvious deformation with wear after use, mostly pale pink such as white.
If you print with a ballpoint pen or ink pen, its characteristics are: poor softness, weak elasticity, low degree of wear after use, so the deformation is not obvious, mainly black.
Characteristics of rubber as a material: taking tires as an example. Features: soft, elastic, no obvious deformation after wearing, black.
Advantages of pencils:
Advantages: it can be altered, the price is low, and the written words are kept for a long time (graphite is relatively stable at room temperature). . (not much)
Disadvantages: The written words are not good-looking (personal feeling), not environmentally friendly (wood), pencil lead is toxic (affecting children's intelligence), and writing is very convenient (not much).
The origin of pencil and eraser pencil
At that time, shepherds in Barodale often used graphite to mark sheep. Inspired by this, people cut graphite blocks into small strips for writing and painting. Soon, King George II of England simply owned the Barodale graphite mine to the royal family, making it an exclusive product of the royal family. Writing with graphite strips will not only dirty your hands, but also break them easily. 176 1 year, the German chemist Faber first solved this problem. He washed graphite with water to make it into graphite powder, then mixed it with sulfur, antimony and rosin, and then made this mixture into strips, which were much tougher than pure graphite strips and less likely to get his hands dirty. This is the earliest pencil.
eraser
Since the birth of 1770, erasers have been loved by everyone for their numerous choices and indispensable stationery roles.
Columbus, who crossed the Atlantic, brought a small rubber ball into an eraser and traveled across the seven oceans to the whole world.
Xiao Qiang bought four pencils and seven erasers with 9 yuan money. As we all know, the price of a pencil is twice that of an eraser. Find the unit price of pencils and erasers, and set X yuan for each eraser and 2x yuan for each pencil.
According to the meaning of the question, you can list the equations.
4*2x+7x=9
15x=9
x=0.6
2x= 1.2
A: Every eraser 0.6 yuan, every pencil 1.2 yuan.
All by hand. I hope I can help you.
Raw materials for pencils and erasers The raw materials for erasers are rubber or plastic pencils.
Graphite pencil: A pencil made of graphite from pencil lead. Can be used for drawing and general writing. Generally speaking, the hardness mark of graphite lead is H for hard pencil, B for soft pencil, HB for pencil with moderate hardness, and F for pencil with hardness between HB and H. Graphite pencils are divided into 6B, 5B, 4B, 3B, 2B, b, HB, f, h, 2H, 3H, 4H, 5H, 6H, 7H, 8H and 9h. The bigger the numbers before the letters, the harder or softer they are, respectively. In addition, there are 7B, 8B and 9B3 soft pencils to meet the special needs of painting.
Colored pencils, colored pencil lead. The lead core consists of clay, pigment, talcum powder, adhesive, grease and wax. Used for marking symbols, painting, drawing charts and maps, etc. Colored pencils are usually packaged in sets (6 12, 24, 36, 64 colors).
Special pencils include glass pencils, color-changing pencils, charcoal pencils, blueprint pencils, watercolor pencils and pastel pencils. They have their own special uses.
① Glass pencil: The lead core consists of pigment, grease and wax. Used for writing or marking on the surface of glass, metal, enamel, ceramics, leather, plastic, plexiglass, etc. , used by industry, medicine, national defense, measurement and other departments. There are red, white, orange, light yellow, purple, dark green, light blue, black and other colors.
2 color-changing pencil: commonly known as copying pencil. The lead core contains dyes such as sun-resistant purple lake, and the handwriting can't be erased with an eraser. It is suitable for writing long-term important documents and recording accounts. There are purple, red, blue, green, yellow and other colors, most of which are violet.
3 carbon pencil: also known as carbon pencil. The lead core is made of clay, charcoal powder, carbon black, etc. Used in painting and oil painting.
4 printing pencil: also known as tracing pencil. The graphite lead core is treated with oil-soluble wax red and other red dyes, which plays a shading role and is used to directly print the picture after drawing.
⑤ Watercolor pen: Acid dyes such as water-soluble acid scarlet are added to the lead core. Dipping lead in water is like watercolor paint, which is used for coloring photos, sketching, drawing maps, statistical charts and so on.
⑥ Pastel pencil: The lead core is made of pigment and porous and soft raw materials (such as calcium carbonate), and contains no grease or wax. Its hardness and writing feel are similar to chalk. Used for painting.
Raw materials Pencil raw materials mainly include pencil shaft raw materials, graphite lead core raw materials, colored lead core raw materials and appearance decoration materials.
The main materials of pencil poles are wood and cement. When making a pen container from wood, it is required that the texture is upright, the structure is fine and uniform, the quality is soft or slightly soft, slightly brittle, contains less resin, has low hygroscopicity, swells and shrinks, and does not deform. There are mainly pencil cypress (red cypress), cedar, cedar, basswood, alder and so on. The adhesive should have proper viscosity, fluidity and wettability. The hardened adhesive layer has toughness, little damage to tools, certain water resistance, heat resistance and aging resistance, easy curing at room temperature, short curing time and no toxicity. There are mainly animal glue, polyester acid vinyl emulsion, hot melt adhesive and so on.
The raw materials and auxiliary materials of graphite lead core are graphite and clay. Graphite is used as a colorant. Using the lubricity and plasticity of lead core, you can draw black marks, stick them firmly on paper and erase them with rubber. Graphite with high carbon content and fine particles should be selected. Clay is a binder, and graphite particles are bonded together by its plasticity and cohesiveness. Clay with good plasticity, low iron content and wide sintering range is needed. Auxiliary materials include molding materials and materials that change the properties of lead cores. Molding materials are used to improve plasticity and adhesion, and improve the formability of lead cores. Commonly used are maltose, tragacanth and so on. The material that change that properties of the lead core are use for oil immersion treatment of the sintered lead core to improve the physical properties of the lead core (such as wear, concentration, stress at the core tip, smoothness, hardness, etc.). ). Commonly used are paraffin, cattle and sheep oil, vaseline, etc. , usually two or more are used together.
The raw materials of colored lead core are pigment, physical raw materials, adhesive, grease and wax. Pigments (including pigments and dyes) play a coloring role, which requires good coloring power, high hiding power, soft texture, high fineness, good heat resistance and non-toxicity. Commonly used are titanium dioxide, carbon black, phthalocyanine blue and so on. Physical raw materials play the role of bonding, skeleton and hardness adjustment.
Exterior decoration materials mainly include nitrocellulose pencil paint, ink, electrochemical aluminum foil, rubber head, aluminum hoop and so on.
It costs 4.98 yuan to buy three pencils and two erasers, and 7.98 yuan to buy five pencils and two erasers. I like to help primary school students solve the unit price of pencils and erasers;
Set pencil x eraser y
3X+2Y=4.98
5X+2Y=7.98
X= 1.5 is obtained.
Y=0.24
Answer; Unit price of pencil1.Unit price of 5 yuan rubber is 0.24 yuan.
1 mechanical pencil and 6 erasers * * * mechanical pencil, 7.2 yuan is twice as big as an eraser. How much are the mechanical pencil and the eraser? 7.2÷(6+ 1×2)=0.9 yuan,
0.9×2= 1.8 yuan
A: mechanical pencil 1.8 yuan, rubber 0.9 yuan.
A pencil with an eraser consists of an eraser and a pencil. 200 words "You are ugly, how ugly you are!" The pencil said proudly.
The eraser was silent and just smiled.
"You are black and white. You are so ugly! " The pencil added.
The eraser said, "Brother Pencil, I am a little ugly, but I am also very useful to my master."
The pencil gave it a disapproving look and said, "What's your use? Without you, I can better help the little master. "
The eraser got angry and said, "How can you work for the master without me?"
The eraser went away. Pencils will be more laborious without erasers. Draw on paper, but there are inevitably mistakes. There is an error, the pencil is frozen. I don't know what to do.
Grandpa put his rubber sister in the pencil box and said to the pencil, "Everyone has his own strengths and weaknesses. We must correctly understand our weaknesses and treat the advantages of others. " After listening to grandpa's words, the pencil bowed its head in shame.
Since then, pencils and erasers have been reconciled.
6 pencils and 4 erasers * * * 10.20 yuan, 3 pencils and 3 erasers * * * 5.4 yuan, 3 pencils and 3 erasers * * * 5.4 yuan →6 pencils and 6 erasers * * * 10.8 yuan.
6 pencils and 6 erasers * *10.8 yuan-6 pencils and 4 erasers * *10.20 yuan →2 erasers 0.6 yuan.
A rubber 0.3 yuan → a rubber 1.5 yuan.
Pencil and eraser farce 1. In the dead of night, the little master's pencil box is very noisy. Do you know why? It turns out that pencils and erasers are criticizing each other respectively!
The thing is, today, the pencil and eraser were playing together, and suddenly the pencil accidentally tripped over the eraser. ...
The eraser quickly picked up the pencil and said, "Brother Pencil, I'm sorry!" " "
But the pencil was ungrateful: "Just say you're sorry!" ! I help the host write every day, stay up late at night, and you sleep every day! "
"You think you are very good! I am also very tired. " The eraser argued, "I help the host get rid of the typo every day." If it weren't for me, the host's homework would be a mess. "
"I am better than you!" "No, I'm fine!" They quarrel with each other. .....
Finally, the pencil proudly said, "If you don't believe that I am better than you, I will prove it to you!" " ! You will rest at home tomorrow, and I will convince you to lose! "
The eraser was smug and said happily, "Then we'll ride a donkey and read a songbook-we'll see!" "
The next morning, Mingming came to the classroom and the teacher asked everyone to write. I mistyped it, but I couldn't find the eraser, so I had to erase it with a pencil. It's dark. That's disgusting!
The teacher saw it when collecting homework, gave Mingming a lecture and wrote a big "poor" word in the homework column.
There are worse things! The math exam is here, and I usually do well in math. I finished my paper at once today. I found a mistake in my careful examination. The teacher stipulates that you are not allowed to borrow someone else's eraser and erase it yourself. Clearly there is no eraser, scratching my scalp, anxious to death, how much the pencil hopes that the eraser will help! But I can't. Finally, I had to paint it out. How ugly it is to be so dark!
Later, the teacher called Mingming to the office and criticized him, and deducted 10 from his paper! Pencil listened to tears in my heart and regretted it! Dare not look up at the master ... ..
After school, Pencil came home depressed and said to the eraser, "Eraser, I'm sorry!"! I shouldn't argue with you, I'm sorry! " Told the story to the eraser quietly.
"Actually ... actually, I'm also at fault." The eraser patted his head and said shyly, "I didn't expect this to happen either." Sorry! " Let's make up! "
"Yes, made up! None of us will leave anyone, help the host together, make the host happy every day and get the best results! " The pencil held the eraser tightly, and finally a smile broke out on his face.
Since then, pencils and erasers have been reconciled. The master obviously won the first place in the city's mathematics competition with their help and their own efforts! In the dead of night, when everyone was asleep, there was a quarrel from a pencil box. It turned out that Brother Pencil and Brother Rubber were arguing about who had more credit.
The little rubber brother proudly said, "I have contributed the most to the whole family." If I dare to recognize the second, no one will dare to recognize the first! " Brother Pencil said, "How can you do this?" You are the youngest in the family. Everyone gives way to you everywhere and takes care of you everywhere. You are still proud! ""I don't care so much! In short, I have the greatest credit! "The little rubber brother said." You are such an ungrateful guy! "The two of them quarreled badly.
Sister chi quickly dissuaded her: "well, stop arguing, everyone is resting!" " "Brother Pencil is not to be outdone:" My contribution is the greatest, and my master can use me to write beautiful words on Uncle Ben's stomach. "The little rubber brother quickly retorted," Have you ever thought that if the master makes a mistake, he can use me to clean it up? " "But without me, you are useless, so my contribution is greater than yours." Brother pencil said proudly. At this point, the pencil and eraser don't know, the ruler sister has woken up all the partners, and everyone discussed a good method. Everyone walked up to them and said with one voice, "Sister pencil box contributed the most. "
Sister ruler took this opportunity to say angrily, "Sister pencil box protects us every day, and we stay in its arms from cold and pain." But so what? But the obscure work, even if it is bitter, can't be said, because it doesn't want to make us sad! Compared with its contribution, you are just insignificant! "
After the persuasion of the ruler sister, my brother and younger brother finally understood this truth and promised not to be conceited in the future and work together with everyone. Since then, this big family has been United to serve everyone. Big brother and little brother have also become good buddies! 3.
One day, the pencil and eraser lying in the pencil box were arguing about who had the greatest credit. Only listen to the pencil proudly say: "I have great credit, the little master will use me every time he does his homework." Without me, he can't finish his homework. " Not to be outdone, the eraser said, "My contribution is great! Every time the young master writes a typo, I will use my white body to clean the wrong place and make it as white as new. " ..... In this way, they argued for a long time. The pencil suddenly said, "Then let's compare and see who has made the greatest contribution in the eyes of the young master." So, the two of them quietly hid.
After a while, the young master came back from the outside and was about to do his homework when he suddenly found the pencil missing. He looked everywhere, but he couldn't find it. He burst into tears and shouted, "Where's my pencil? Where is it? " Pencil heard the little master calling his name anxiously and ran out at once. When the young master saw it, he stopped crying and said to the pencil, "Where have you been? I can't find you. " I'm dying. The pencil is very proud of what the little master said. I think: I have made the greatest contribution to young master. Young master began to do his homework, not long after. He found that he had written wrong words. He just wanted to get the eraser, but he found it was gone. He hurried to look for it, but he couldn't find it. He was so anxious that he began to cry again and shouted, "where is my eraser?" Where is it? "Rubber heard the little master calling its name anxiously and ran out in a hurry. When the young master saw it, the tears stopped and a bright smile appeared on his face. He said to the eraser, "Where have you been? I can't find you anywhere. I am worried to death. " Eraser is also very proud. I think: I have made the greatest contribution to young master. But superfine product said to the pencil and eraser, "I can't write without a pencil, and I can't correct my mistakes without an eraser. After listening to the little master's words, the pencil said to the eraser in shame, "Although I can write on paper, I can't erase the wrong words." "You can find out the typo." The eraser also said shyly, "I can erase the typo, but I can't write it, but you can write it." We all have our own strengths and weaknesses.
Through this incident, pencils and erasers understand a truth: they should learn from each other's strengths. Young master has a pencil, but he has written wrong words. He can't do without an eraser. They are equally important to the young master and are indispensable. Since then, pencils and erasers have become inseparable friends.
What's the name of the pencil with eraser? Just call it a pencil = =