c - 我尝试制作一个计算电价的c语言程序，但是一行行不通

Question

我尝试编写一个计算电价的c语言程序，但是一行行不行。

这是我的代码。

#include <stdio.h>

int main()
{
    int usageElectric;      //amount of electricity used
    int basicMoney;         //basic price
    int totalMoney;         //total price
    double usageMoneyPerKw; //kw per used price
    double totalFinalMoney; //final usage price
    double tax;             //tax


    printf("put in the amount of electricity used (kw) : ");  //put in 150kw.
    scanf("%d", &usageElectric);

    basicMoney = 660;   //basic price = $660
    usageMoneyPerKw = 88.5; //kw per usage price : $88.5
    totalMoney = basicMoney + (usageElectric * usageMoneyPerKw);    

    tax = totalMoney * (9 / 100);   //This line is the problem line = doesn't work

    totalFinalMoney = totalMoney + tax; 

    printf("Tax is %d\n", tax);  // a line to show that the tax isn't being caluculated properly

    printf("The final usage price is %lf.", totalFinalMoney);

    return 0;
}

如果输入为 150(kw)，则 TotalFinalMoney 应为 $15189.150000

任何人都可以帮我解决为什么这条线不起作用吗？

tax = totalMoney * (9 / 100);

如果工作正常，结果应该如下:

tax = 13935 * (9/100) = 1254.15

因此，最终结果应该是:

The final usage price is 15189.150000

Answer 1

在子表达式 9/100 中，两个操作数都是整数，因此除法是整数除法，这意味着任何小数部分都会被截断，因此计算结果为 0。

如果更改为浮点常量，您将得到浮点除法。因此将上面的内容更改为:

9.0/100.0

或者简单地说:

0.09