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Sample Solution:

Write a Java program to print the area and perimeter of a circle.

In geometry, the area enclosed by a circle of radius r is πr². Here the Greek letter π represents a constant, approximately equal to 3.14159, which is equal to the ratio of the circumference of any circle to its diameter.

The circumference of a circle is the linear distance around its edge.

Pictorial Presentation:

Why is the area of a circle of a circle pi times the square of the radius? 

Java Code:

import java.util.Scanner;
public class Main {
 public static void main(String[] args) {
  Scanner io = new Scanner(System.in);
  System.out.println("Input the radius of the circle: ");
  double radius = io.nextDouble();
  System.out.println("Perimeter is = " + (2 * radius * Math.PI));
  System.out.println("Area is = " + (Math.PI * radius * radius));
 }
}

Output:

Input the radius of the circle:   5 
Perimeter is = 31.41592653589793 
Area is = 78.53981633974483 

Flowchart: