For the second grade math problems, children are usually asked to estimate the quantity of one item, so as to cultivate their perceptual knowledge of numbers and intuitive feeling of quantity. For example, the teacher may ask, "How many students are there in your class? Please estimate whether it is dozens or hundreds? "

At this time, children can estimate according to their own impression of class size. For example, if a child knows that there are 20 students in the class, he can estimate that the answer is between twenty and thirty. It is suggested that children can narrow the estimation range to two numbers, such as 20~30, and then further narrow it. This can make children feel the relationship between numbers and cultivate their mathematical intuition and logical thinking ability.

As follows:

Calculation, in mathematical terms, is a kind of thinking process that transforms a single or complex input value into a single or complex result. The definition of calculation can be used in many ways, from a fairly precise definition, such as "arithmetic" using various algorithms, to a more abstract definition, such as "calculation of strategy" or "calculation of the success probability of the relationship between two people in the competition".

7 times 8(7x8) is a simple arithmetic. Calculations in mathematics include addition, subtraction, multiplication, division, multiplication, root and so on. Addition, subtraction, multiplication and division are called four operations. It is a complex operation to calculate the fair price in financial evaluation with Black-Scholes model.

The election results (opinion polls) evaluated from the calculation of voting intention also contain some arithmetic, but the results provided are "the range of various possibilities" rather than a single correct answer.

The way to determine how to establish a relationship between people is also the result of a calculation, but this calculation is difficult to be accurate, unpredictable or even clearly defined. This definition of calculation with infinite possibilities is completely different from the mathematical arithmetic mentioned above.

Calculation in English is "calculation", which comes from Latin "Calculus" and refers to the small stone used for calculation on the abacus.