When primary school students add two-digit numbers in vertical form, the ones digit should be aligned with the ones digit, and the tens digit should be aligned with the tens digit. Start adding from the ones digit, and when the ones digit is added to 10, add 1 to the tens digit. What is the 1 that goes to the tens place? Many children may not really understand it, they are just told to do it by the teacher.
How is the two-digit number 12 formed? What does 1 stand for, and what does 2 stand for?
To answer these questions, we have to start with the digits of numbers and the decimal system. Parents are more concerned about their children's calculation ability. They might as well clarify the following basic things first, which is worth studying 10 pages of calculation questions.
①Number name, units, tens, hundreds, thousands.
② Understand the counting rules of decimal and know the decimal relationship between different digits, that is, 10 ones is ten, 10 tens is one hundred, and 10 hundreds is one thousand...
Maybe you will think of the two above It's very simple. If you ask your children, they can answer it. What you can tell may not necessarily be useful. How many children rely on memory?
Our aim is still to follow the concrete thinking of school-age children, and to operate and demonstrate intuitively.
1, Montessori teaching aids
If you want to talk about which concrete operation is better, it is Montessori teaching!
Montessori hopes to help children understand the decimal system in mathematics through practical manipulative materials, so she designed these beads teaching aids in the picture below to help children understand. It intuitively shows that "10 1s are 10, 10 10s are 100, and 10 100s are 1000." Turn abstraction into something concrete that children can directly perceive.
① Quantity understanding
From left to right are 1000, 100, 10 and 1. Introduced in order starting from 1.
"This is 1."
"This is 10, 1 1, 2 1, 3 1...10 1, 10 1 is 10."
"This is 100, 1 10, 2 10s, 3 10s... 10 10s, 10 10s is 100. "
" is 1000, 1 100s, 2 100s, 3 100s... 10 100s is 1000. . ”
② Understanding numbers
introduces the numbers 1, 10, 100, and 1000 in order, allowing children to identify how many 0s there are in ten, how many 0s there are in a hundred, and how many 0s there are in a thousand. Stack the cards together and guide the child to read 1111.
③ Combination of quantities
Any combination of a number will give the corresponding quantity representation; or any combination of quantities will be given and the corresponding numerical representation will be given. The ones digit represents the number of scattered beads, the tens digit of represents how many 10s there are, and the hundreds digit represents how many 100 there are. Children may think that there are so many beads in the tens and hundreds, how can they be 3 and 2? must emphasize that the string of tens and the board of hundreds are all one whole.
④ Transposition game
If there are 5 more beads in 237, how many will there be? There are 7 scattered beads in
237. Five more beads will make it 12. Use 10 ones for a ten. Put the exchanged tens into the tens place beads, leaving 2 in the ones place. There are 2 units digits, 4 tens digits, and 2 hundreds digits at the end, which is 242.
If 242 wants to take away 50, the tens place is only 40. If it is not enough, one hundred boards must be replaced by 10 tens.
If you don’t have these Montessori teaching aids, don’t worry. Small sticks, branches, and toothpicks can be used instead. Bundle up to 10 in a bundle. Isn’t that what we did when we were kids? It's just that the workload is a little larger, and numbers within 100 can be bundled together.
2, " Khan Academy " glass ball jar method
"Khan Academy" is a free learning video created by Bangladeshi-American Salman Khan with a large number of teaching videos, including mathematics, science, financial economics, Computers, arts and humanities, etc., several classes cover all stages and fields of a person's education. Interested students should not miss it, you deserve it! The key is free, free for life!
Mathematics covers everything from counting, addition, subtraction, multiplication and division to calculus and advanced mathematics. Several of the lessons were also about numbers. Khan cleverly used the process of sorting glass balls to explain numbers and the decimal system.
10 pieces are put into a purple jar with a capacity of 10 (ten-ball jar).
10 glass balls from a ten-ball jar fit exactly into an orange jar with a capacity of 100 (a hundred-ball jar).
10 glass balls from the one-hundred-ball jar fit exactly into a green jar with a capacity of 1,000 (thousand-ball jar).
Suppose there are a lot of glass balls in the bag. After filling 2 thousand-ball jars, it is estimated that there are less than 1,000 glass balls in the bag; replace it with a smaller 100-ball jar. After filling 4 100-ball jars, ; The remaining is less than 100, use ten-ball cans, fill 3 ten-ball cans, and finally there are 6 scattered ones left. This reduces the workload of counting. Then the total sum is 2000+400+30+6=2436, which is read as two thousand four hundred and thirty-six.
The way of thinking of the glass sphere jar is the same as that of Montessori. Both use practical operations to intuitively express the relationship between numbers such as ones, tens, hundreds, thousands and so on.
Correctly understand the concept of digits and know that adding 10 to 10 is the basis for doing two-digit addition and subtraction.
For example, 41-26, operate as follows. Children in kindergarten can also quickly understand that the ones digit is not enough to reduce, borrow a 10 from the tens digit, and become 11, 11-6=5; the tens digit becomes 3, corresponding Reduce the remaining 1. The final result is 15.
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I have a four-and-a-half-year-old child at home, and I am concerned about mathematical enlightenment~
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