The first part: math diary, the second grade of primary school-a puzzling math problem.
I saw a puzzling math problem tonight. The topic is: 37 students want to cross the river. There is an empty boat at the ferry that can only take five people. How many times must they cross the river with this boat at least?
Careless people often ignore the "empty boat", that is, they forget to have punting, so they can only sit four people at a time. In this way, 37 people subtract one rowing classmate, leaving 36 students, 36 divided by 4 equals 9, and the classmate who worked as a boatman on the other side for the last time also landed 4, so it takes at least 9 trips.
Part II: math diary II, Grade Two in Primary School-A Math Problem.
I met another math problem today, and it took me a lot of effort to solve it. The topic is: there are 30 birds in two trees, and 4 birds fly away from the second tree first. At this time, tree A flew to tree B with three birds, and the birds on the two trees were just equal. How many birds are there in each tree?
As soon as I saw the topic, I knew it was a reduction problem, so I solved it by the method of reduction problem. But when I checked, I found something was wrong. I will do it again more seriously. I think there are as many as four missing, half of them are 13, and the restored B-tree is14; A tree is 16. The formula is: (30-4) ÷ 2 = 13 (only); 13-3+4 =14 (only); 30- 14 = 16 (only). The answers are: a tree 16 and b tree 14.
By solving this problem, I understand that no matter what I do, I should be careful, otherwise, even if I master the solution to the problem, the result will be wrong.
Chapter Three: math diary, Grade Three and Grade Two —— The Problem of Eating KFC.
Today, my family went to KFC in Longgang for a family meal.
When we get there, people are always crowded. We finally ordered good food and found a seat to sit down. Here comes the food. This is a sumptuous set meal. There are 12 drumsticks in it. I thought: how to divide it equally? Then I remembered the division of 12÷3=4. We each have four drumsticks. Later, I ate my mother's 1 chicken leg and my aunt's two chicken legs. My aunt said, "You can't eat this for free. I ask you, how much did you eat? " How many more servings do you have to eat before you can finish them all? "I thought about it and replied," I ate 7/ 12, and then I ate 5/ 12. I ate all of it. "Fortunately, I learned the knowledge of fractions and can answer the questions correctly.
Chapter Four: math diary IV in Grade Two of Primary School-Apple Tree Problem.
In the evening, I saw a problem in the Olympiad Book: the number of apple trees in the orchard is three times that of pear trees. Master Lao Wang fertilizes 50 apple trees and 20 pear trees every day. A few days later, all the pear trees were fertilized, but the remaining 80 apple trees were not fertilized. Excuse me: How many apple trees and pear trees are there in the orchard?
I am not intimidated by this question, but it can stimulate my interest. I think the apple tree is three times as big as the pear tree. If two kinds of trees are to be fertilized on the same day, Master Lao Wang will fertilize "20×3" apple trees and 20 pear trees every day. In fact, he only fertilizes 50 apple trees every day, which is 10, and the last 80 trees. Therefore, Master Lao Wang has been fertilizing for 8 days. 20 pear trees a day, 8 days is 160 pear trees. According to the first condition, there are 480 apple trees. This is to solve the problem with the idea of hypothesis, so I think the hypothesis method is really a good way to solve the problem.
The fifth part: math diary in the second grade of primary school-calculating tuition.
Today, after I signed up for school and went home, I wrapped the book cover and began to calculate the cost of this semester.
The first is tuition. Tuition fee is 4 10 yuan, plus drinking water fee in 20 yuan, 430 yuan. Next, the charge of the Olympic Mathematics School is 180 yuan. It is estimated that the bus fare is in 20 yuan and ***200 yuan. There is also money to buy exercise books: 2 copies of "Classpass" 2 1.5 yuan; English practice 1 9.9 yuan; 2 copies of Examination Paper Course Pass 15.9 yuan; "Jiangsu Big Test Paper" 3 copies 2 1 yuan. 21.5+9.9+15.9+13+21= 81.3 (yuan).
Study fee: 430+200+81.3 = 711.3 (Yuan).
Living expenses: I will drink about 5 cases of milk this semester, 5×30= 150 yuan. Every meal is about 2~3 yuan, of which 2.5 yuan is 2.5×3×30×5= 1 125 (yuan). "What else?" I bit my pencil and said to myself, "and your school supplies." Hey, mom's home. Yes, and school supplies.
School supplies: a pencil-box 8 yuan, a pencil-box 3 yuan (very cheap, clearance goods), six pencils 3 yuan, an eraser 0.5 yuan, two triangular rulers 1 yuan, two mechanical pencil 5 yuan, 8+3+0.5+ 1+5=20.5 (yuan).
Total expenditure: 711.3+150+1125+20.5 = 2006.8 (yuan).
Wow, I didn't expect that I, who usually don't spend much money, would let my parents spend 2006.8 yuan this semester. It seems that I will save money!
Chapter 6: math diary VI, Grade Two in Primary School —— Interesting multiplication calculation.
Today, we went to a friend's house for dinner. We saw a lot of delicious drooling. We see that a table can seat four people, and three people are just full. I counted: 3X4= 12 (people), so there are 12 people in total. After dinner, my friend gave us two apples each, and I calculated again: 65438. What a good multiplication you learned today!
Article 7: math diary in the second grade of primary school-buy breakfast.
This morning, my mother and I went to buy breakfast.
When I arrived at the hotel, I asked my uncle, "How much is a fried dough stick? How much is a bag of soybean milk? " My uncle said kindly, "A fried dough stick costs fifty cents, and a bag of soybean milk costs fifty cents." At this time, my mother asked me a question: "A fried dough stick and a bag of soybean milk are fifty cents, so how much does it cost to buy five fried dough sticks and five bags of soybean milk?" At this time, I thought about it carefully. 5525, 2×25=50, equals 5 yuan. Mom added, "There is a simpler way. Think again! " "I patted my head, thought for a moment, and finally figured it out. I am happy to tell my mother: "1 root fried dough sticks and 1 bag of soybean milk need 1 yuan, and one fried dough sticks and a bag of soybean milk is 1 serving, so five portions are not 5 yuan money! My mother gave me a thumb and said, "Son, you are great! " "
Mathematics used to be so profound, so interesting and so important that we could apply a lot of knowledge from our daily life. We must learn math well, not only other math courses are also important.
In short, we must study hard and make progress every day!
Chapter 8: math diary, Grade Two in Primary School-Happy Rubik's Cube.
On Saturday, I fiddled with the Rubik's cube in my hand. I stumbled across that the Rubik's Cube has six sides. The teacher just said: the four sides of a square are equal. I measured the side length of the Rubik's cube with a meter ruler. My mother asked me to calculate the circumference of a face? I thought for a moment, and I got it. It should be 6× 4 = 24 (cm). I also found that the Rubik's Cube has 24 corners. The formula is: 6× 4 = 24 (pieces)
More interestingly, there are 9 small squares on one side of the Rubik's Cube and 9 small squares on the opposite side. How many small squares are there on the surface of a cube? 6× 9 = 54 (pieces). How many cubes does this Rubik's Cube consist of? 3× 9 = 27 (piece)
Rubik's cube in hand, endless happiness!