Getting average problem

[wharp2]

Hello, I am having a bit of a beginner problem :) In my code my average is not coming out to be right. Bellow is my code and the out put. Thanks for the help!

//  main.cpp
//  Program 8
//  Created by William Blake Harp on 7/16/14.

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int main()
{
    double average = 0;
    double class_average = 0;
    int sum_of_test_scores = 0;
    
    //2D Array.
    const int students = 5;
    const int test_scores = 4;
    int scores[students][test_scores];
    
    //Arrays on the heap.
    string* arrayNames = nullptr;
    arrayNames = new string[students];
    
    int* arrayID = nullptr;
    arrayID = new int[students];
    
    int* arrayAverage = nullptr;
    arrayAverage = new int[students];
    
    int* arrayLetterGrade = nullptr;
    arrayLetterGrade = new int[students];
    
    ifstream inputFile;
    
    // Open the file.
    inputFile.open("Student Data.txt");
    
    // do an initial test.
    cout<<boolalpha;
    cout<< "Is the file good? --> "<<inputFile.good()<<endl<<endl;
    
    if (inputFile.fail())
        cout << "Can't open the file!" << endl;
    
    else
    {
        for( int i(0); i != 5; i++ )
        {
            // read name.
            getline(inputFile, arrayNames[i]);
            cout<<arrayNames[i]<<endl;
            
            // read student id.
            inputFile >> arrayID[i];
            cout<< arrayID[i] <<endl;
            
            // read four(4) scores.
            for( int j(0); j != 4; j++ )
            {
                inputFile >> scores[i][j];
                cout << scores[i][j] << endl;
            }
            
            string str;
            
            // consume '\n' char (Use getline for mac/Xcode!!!).
            getline (inputFile, str);
            
            
            cout << "I have read "<<i+1 <<" record/s\n\n";
        }// end read loop.
        
        // display student name, score, ID and average.
        for( int i(0); i != 5; i++ )
        {
            cout << arrayNames[i];
            
            for( int j(0); j != 4; j++ )
            {
                cout << scores[i][j] << " ";
                
                sum_of_test_scores += scores[i][j];
            }
            cout << endl;
            
            average = sum_of_test_scores / 5.0;
            cout << "The average is: " << average << endl;
            
            if (average > 100)
            {
                cout << "invalid average for grade please try again." << endl;
            }
            else if(average >= 90 && average <= 100)
            {
                cout << "Letter grade is A!" << endl;
            }
            else if (average >= 89 && average <= 80)
            {
                cout << "Letter grade is B" << endl;
            }
            else if (average >= 79 && average <= 70)
            {
                cout << "Letter grade is C" << endl;
            }
            else if (average >= 79 && average <= 60)
            {
                cout << "Letter grade is D" << endl;
            }
            else
            {
                cout << "Letter grade is F!" << endl;
            }

            cout << endl;
            
        }// End display name & scores.
        
        cout << endl;
        
        // Loop for class average.
        for (int i = 0; i != 5; i++)
        {
            class_average = sum_of_test_scores / 5.0;
            
        }
        cout << "The class average is: " << class_average << endl;
        
        // Close the file.
        inputFile.close();
        
        // releasing memory block on the heap.
        delete [] arrayNames;
        arrayNames = 0;
        delete [] arrayID;
        arrayID = 0;
        delete [] arrayAverage;
        arrayAverage = 0;
        delete [] arrayLetterGrade;
        arrayLetterGrade = 0;
    }
    return 0;
}// End Code. 

Is the file good? --> true

Amy Adams
10111
97
86
78
95
I have read 1 record/s

Ben Barr
20222
89
81
73
87
I have read 2 record/s

Carla Carr
30333
79
71
63
77
I have read 3 record/s

Don Davis
40444
69
62
58
67
I have read 4 record/s

Edna Eaton
50555
63
51
62
48
I have read 5 record/s

Amy Adams
97 86 78 95 
The average is: 71.2
Letter grade is F!

Ben Barr
89 81 73 87 
The average is: 137.2
invalid average for grade please try again.

Carla Carr
79 71 63 77 
The average is: 195.2
invalid average for grade please try again.

Don Davis
69 62 58 67 
The average is: 246.4
invalid average for grade please try again.

Edna Eaton
63 51 62 48 
The average is: 291.2
invalid average for grade please try again.


The class average is: 291.2

[admkrk]

This is one reason magic number are bad
average = sum_of_test_scores / 5.0;
should be
average = sum_of_test_scores / test_scores;
then you would not make the mistake of putting the wrong number for the divisor.

Also sum_of_test_scores is not reset to 0 so it just keeps adding up all the scores.
((97 + 86 + 78 + 95) + (89 + 81 + 73 + 87)) / 5.0 = 137.2

[wharp2]

how would you reset it to 0? Could you show me?

[admkrk]

sum_of_test_scores = 0;
I would do it after the average is calculated. You are also going to need another variable to keep a running total of all the scores in order to get the class average. Obviously you need to add the sum to that variable before resetting it also.