This kind of question usually gives a numerical range, so that students can "guess" what the specific answer is. So, how to calculate skillfully? Share a practical method!
Take the topic as an example:
Let's look at the seventh question in the picture. The conditions given in the title are: second-grade students perform dances in a square formation, but the number is unknown. Only the number is more than 60, less than 70. The question is: How many students are dancing?
For the second-year students, this kind of topic belongs to extended application, and the difficulty coefficient is relatively large.
So, how to calculate?
The analysis idea is this:
The first step is to find the conditions given by the topic.
There are two conditions. The first condition is that the formation is square, the second condition is that the total number of people is between 60 and 70.
The second step is to think about the solution.
The multiplication formula is basically finished. However, the product of two multiplication formulas is between 60 and 70: 8864 and 796 13. The results of these two formulas are between 60 and 70.
With this idea, we should start thinking, which formula is the key to solve the problem?
Think about the square of the formation again, and the answer comes out. Since it is a square, it means that the two multipliers are exactly the same. Therefore, the answer must be 8×8 = 64.
In fact, the clever calculation method is to find the appropriate multiplication formula according to the analysis of conditions.
For example, the number of apples in the above question is between 30 and 40. What number is it?
The title also gives a condition that apples are packed in 8 plates, each plate has the same number. Then, students will continue to think with multiplication formula.
According to the conditions and questions, we can get a formula:? x8=30~40。
Four, eight, three, twelve, five, eight, forty.
Analyzing these two sentences carefully, the answers are four, eight, three and twelve. Therefore, there are four plates of apples and the number of apples is 32.
Senior two students, when encountering such problems, can improve their mathematical thinking ability if they can use their brains to think according to the methods taught by their teachers.
Now that you have learned the method, students might as well pursue the victory, and then answer the questions in the picture above to see if you can get the answer soon:
Aunt Zhang's tour group can fill three identical tables, leaving two people without seats. How many people did she bring? Students, you can count the chairs on this table first, then decide the number of seats, and then consider how to solve them.