Calculating a percentage

This is a discussion on Calculating a percentage within the C++ Programming forums, part of the General Programming Boards category; I have to a small assignment, and I am stoked on the last part. I basiclly have to find 9 ...

  1. #1
    Its hard... But im here swgh's Avatar
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    Calculating a percentage

    I have to a small assignment, and I am stoked on the last part. I basiclly have
    to find 9 percent of any number entered by the user and then add 200 to it.
    I will not post the assignment code cause its huge but I have created a small
    dummy program to see if I can get the calculation correct. I have never been good at percentage calculations lol.

    This is my best effort, it compiles but its the wrong output. What changes do I have to do to make the output correct?

    EDIT: Read the comment above the static_cast for an idea.

    Code:
    #include <iostream>
    
    using std::cout;
    using std::endl;
    using std::cin;
    using std::fixed;
    
    #include <iomanip>
    
    using std::setprecision;
    
    // main function - driver
    int main ( void )
    {
       double sales; // total sales made for the week
       double salary; // salary for each employee
       
       cout << "Enter sales in pounds ( enter -1 to quit ): ";
       cin >> sales;
       
       while ( sales != -1 )
       {
          // calculate salary- each employee
         // gets 200 standard and 9% of sales
          salary = static_cast < double > ( sales ) / 0.9 + 200; 
    		
         cout << "\nSalary is: " << setprecision( 2 ) << fixed << salary; 
          
          cout << "\n\nEnter sales in pounds ( enter -1 to quit ): ";
          cin >> sales;
       }
       
       cin.get(); // freeze console output window
       
       return 0; // indicate program ended sucsesfuly
    }
    I'm just trying to be a better person - My Name Is Earl

  2. #2
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    First, you are casting 'sales' to double and it's already a double so that's a completely useless cast. Second, you should multiply by 0.09 (not 0.9, this is 90%) instead of dividing.

  3. #3
    Its hard... But im here swgh's Avatar
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    Doh! Thanks Desolation!

    I think I need to back to primary school!
    I just noticed about the cast, I thought i delcared sales as an int. I got rid of the cast and it worked like a charm. Thanks for the help
    I'm just trying to be a better person - My Name Is Earl

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    [edit]sry, i didnt c it in desolations post[/edit]

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