In this **HackerRank Day 1: Let and Const 10 days of javascript problem solution** Declare a constant variable, PI, and assign it the value Math.PI. You will not pass this challenge unless the variable is declared as a constant and named PI (uppercase).

Read a number, r, denoting the radius of a circle from stdin.

Use PI and r to calculate the area and perimeter of a circle having radius r.

Print area as the first line of output and print perimeter as the second line of output.

## Problem solution in JavaScript programming.

function main() {
// Write your code here. Read input using 'readLine()' and print output using 'console.log()'.
const PI = Math.PI;
let r = readLine();
function area(PI,r) {
area = PI * (r *r);
console.log(area);
}
function perimeter(PI,r) {
perimeter = 2 *PI * r ;
console.log(perimeter);
}
// Print the area of the circle:
area(PI,r);
// Print the perimeter of the circle:
perimeter(PI,r);