减法给了我积极的结果 C++

Question

if (GoalWeight < 0.0) {
    int weeks;
    cout << "How many weeks do you plan to continue this trend?\n";
    cin >> weeks;
    double NewWeight = GoalWeight * weeks;
    double NegBMI = (weight - NewWeight) * 703 / (pow(HeightConverter, 2));
    cout << "If you complete your plan for " << weeks << "weeks you will have a new BMI of: \n" << NegBMI;
}
system("pause");
return 0;

}

输出结果：

What is your current weight?: 180

What is your current height in inches?" 71

Your current BMI is: 25.10(Not part of output, but this is correct)

What is your goal weight change?(lbs) -1.5

How many weeks do you plan to continue this trend?: 6

If you complete your plan for 6 weeks you will have a new BMI of: 26.36

你可以看出这是错误的

BMI 的计算方法是（体重 * 703）/身高^2（英寸）

它对负数的作用是：

180 + 9(instead of 180 - 9) giving (191 * 703) / 71^2 yielding 26.36

而不是：

180 - 9(giving 171 * 703) / 71^2 yielding the correct output of:23.84

我知道你们都在摇头说我一定是个白痴，这是理所当然的，我希望有人能帮助我！

Answer 1

What is your goal weight change?(lbs) -1.5

How many weeks do you plan to continue this trend?: 6

6 * ( -1.5 ) == -9
180 - (-9) == 189

因此，您要么将目标体重变化输入为正数，要么将其相加，而不是相减。

Answer 2

由于你的语句 6 * -1.5，你的 newWeight 结果为 -9。如果你想减去它，只需制作 (weight + newWeight) 而不是 -。

Answer 3

您是否相信如果您这样做 (+NewWeight) NewWeight 的值变为正值？

事实并非如此：

一元加运算符（+）：对数字类型的运算结果是操作数本身的值。此运算符已为所有数字类型预定义。

作为解决方案，使用 Reginalds 的想法并制作 (weight + newWeight) 而不是 -。

减法给了我积极的结果 C++

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