Help me in solving CLB026 problem

My issue

why to use double instead of float

My code

#include <stdio.h>

int main() {

  float pi = 3.14;
  float radius = 8.9;      //radius has to be declared as a 'double'
  float area = pi * radius * radius;

  printf("The Area of the given Circle is %f", area);
  return 0;

Learning course: Learn C
Problem Link: CodeChef: Practical coding for everyone

Cozz its mentioned in the question itself to use double.