"Area of ​​a Circle" PPT courseware on the circumference and area of ​​a circle

Description

"Area of ​​a Circle" PPT courseware on the circumference and area of ​​a circle

teaching objectives

1. Combined with specific examples, experience the process of understanding circles and using different methods to calculate the area of ​​a circle.

2. Be able to calculate the area of ​​a circle using their own methods and be able to solve simple problems related to the area of ​​a circle.

3. Further understand the close connection between mathematics and life, and gain experience and methods for comprehensively applying the learned knowledge to solve practical problems.

There is a circular fountain with a radius of 3 meters in a park. There is a 1 meter wide corridor around the fountain. How many square meters does Yonglu cover?

Think about it, how to calculate the area of ​​a circular corridor?

(1) The area occupied by the fountain and the corridor:

3.14×(1+3)²＝3.14×16＝50.24(square meters)

(2) The area occupied by the fountain:

3.14×3²＝3.14×9＝28.26(square meters)

(3) The area occupied by Yong Road:

50.24-28.26＝21.98 (square meters)

Answer: The area of ​​Yonglu is 21.98 square meters.

The cross-section of a cast iron part is annular, with an outer radius of 20 cm and an inner radius of 16 cm. What is the area of ​​the ring in square centimeters?

3.14×（20²－16²）

=3.14×144

=452.16 (square centimeters)

3.14×20²-3.14×16²

=1256-803.84

=452.16 (square centimeters)

Answer: The area of ​​the ring is 452.16 square centimeters.

In conclusion

1. The part between two concentric circles with different radii is the ring.

2. Subtract the area of ​​the inner circle from the area of ​​the outer circle to find the area of ​​the ring. If S is used to represent the area of ​​the ring, the calculation formula for the area of ​​the ring is S=πR²-πr² or S=π(R²-r²).

practice

1. Take a photo of a CD, point out the ring on the CD, measure the relevant data, and calculate the area of ​​the ring.

2. Take a paper fan, first measure the width of the fan handle and the paper surface, and then calculate the area of ​​the paper surface after the fan is opened.

3. Calculate the area of ​​the colored parts of each picture. (Unit: cm)

3.14×（6²－3²）

=3.14×27

=84.78 (square centimeters)

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For more information about the "Perimeter and Area of ​​a Circle and the Area of ​​a Ring" PPT courseware, please click the "Perimeter and Area of ​​a Circle ppt Area of ​​a Ring ppt" tag.

File Info

Update Time: 2024-10-18

This template belongs to Mathematics courseware Hebei Education Edition Sixth Grade Mathematics Volume 1 industry PPT template

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