1, compare the sizes of 3 and 5:? 3+5=8, so 3 is less than 5, 3-5=-2, so 3 is less than 5.
2. Compare the sizes of 6 and 4: 6+4= 10, so 6 is greater than 4 and 6-4=2, so 6 is greater than 4.
3. Compare the sizes of 7 and 9: 7+9= 16, so 7 is less than 9, and 7-9=-2, so 7 is less than 9.
It should be noted that the results of addition and subtraction are not necessarily the same, so when comparing the sizes of two numbers, you need to add and subtract according to the specific situation to get the results.
The origin of addition and subtraction
The origin, addition and subtraction of 1 can be traced back to ancient times, and specific historical records can be found in ancient Egypt, ancient Greece, ancient India and other civilizations in the history of mathematics. In the Moscow papyrus of ancient Egypt, the problem of calculating fractions and geometric figure areas by addition and subtraction was mentioned.
2. In China, the origin of addition and subtraction can be traced back to the Spring and Autumn Period and the Warring States Period, when the "99 multiplication table" appeared to perform basic mathematical operations. With the development of mathematics, addition and subtraction has gradually become one of the basic skills of mathematical operation, which plays an important role in ancient mathematics in China.
3. In Europe, the development of addition and subtraction can be traced back to the Middle Ages, and European mathematicians began to study mathematical symbols and mathematical operation rules. The British mathematician Oughtred invented the multiplication symbol "×" in 163 1, and used the addition and subtraction symbols "+"and "-"to indicate addition and subtraction.
At the same time, the development of addition and subtraction is progressing with the development of industry and commerce. In business and industry, addition and subtraction are widely used to calculate quantity, weight, length, etc., and become the basic operation skills in these fields.
5. The origin and development of addition and subtraction are closely related to the progress in mathematics, commerce, industry and other fields. The historical background and cultural connotation of addition and subtraction are rich and colorful, which is an important part of the development of human civilization.