"Constants and Variables in Life" PPT courseware

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"Constants and Variables in Life" PPT courseware

The wise crow realizes:

1. The size of the bottle mouth cannot be changed, nor can the amount of water;

2. But the height of the water in the bottle can be changed. The more stones you throw, the higher the water level will be.

When we analyze various phenomena in the real world from a mathematical perspective, we will encounter a variety of quantities, such as:

Speed, time and distance in motion of an object;

Radius, circumference and pi of a circle;

The quantity, unit price and total price of the purchased goods;

The changing temperature of a city at various times of the day;

The water level in a certain section of river changes throughout the day;

…

In a certain process, some quantities are fixed and some are constantly changing.

Do the math:

1. The formula for the area of ​​a circle is S=πr2. Take some different values ​​of r and calculate the corresponding value of S:

In the process of calculating the area of ​​circles with different radii, which quantities are changing and which quantities are constant?

2. Xiao Ming works as a part-time worker in the work-study program, and the salary standard is 25 yuan/hour. Assume that when the number of hours he works is t, the amount of salary he deserves is m yuan, then m=25t.

Take some different values ​​of t and find the corresponding value of m:

In the process of calculating the amount of salary Xiao Ming deserves based on different hours worked, which quantities are changing and which quantities remain unchanged?

concept

1. In a process, a fixed quantity is called a constant.

Which of the above two questions are constants?

2. In a process, quantities that can take on different values ​​are called variables.

Which of the above two questions are variables?

2. We know: distance = speed × time, that is, S = vt.

(1) If the car is traveling at a speed of 50 kilometers/hour, what are the constants and variables?

The constant is 50 kilometers/hour; the variables are S, t.

(2) If the car travels 200 kilometers, what are the constants and variables?

The constant is 200 kilometers; the variables are v, t.

(3) If the car drives for 4 hours, what are the constants and variables?

The constant is 4 hours; the variables are S, v.

Note: Constants and variables are not absolute but relative to a certain change process.

Can you predict your future height?

If a and b respectively represent the height of the parents, h male and h female respectively represent the height of the child as an adult, then there is a relationship: h male = 0.54 (a + b )

h female = 0.54 (0.975a+b)

What are the constants here? What are variables?

The relationship between the circumference C and the radius r of a circle is ______, the constant is ______, and the variable is ______.

In the physical education class, in the 400m running test, in the relationship between the time t (seconds) spent by the students and the average speed v (meters/second), the constant is ______ and the variable is _____________.

Class summary

1. What did you gain from this class?

(1) Use one variable to represent another variable.

(2) The concepts of variables and constants.

2. Do you have any questions?

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"Constants and Variables in Life" PPT Courseware 2:

"Constants and Variables in Life" PPT Courseware 2 S=vt, V=1.5 km/min Question: From this process, you discovered which quantities are fixed and which quantities are constantly changing? In the process of calculating the total fare based on different number of people, which quantities are changing and which quantities are not...

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Update Time: 2024-09-14

This template belongs to Mathematics courseware Qingdao Edition Seventh Grade Mathematics Volume 1 industry PPT template

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