学习笔记习题3.3

#include<stdio.h>
#define price 5
int main(){

   // const int price = 5 ;
    int shuliang = 0 ;       
    printf(" 请输入一个数值！");
   
    scanf("%d" ,&shuliang);

    if(shuliang >= 20 ){
        printf("%.2f",(float)shuliang *  0.9 * price );
    }else if(shuliang >= 50 ){
            printf("%.2f",(float)shuliang *  0.7 * price );
    }else{
            printf("%d", shuliang * price );
    }
    return 0 ;
}