Why my function not working?

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Why is my function not working? why I am getting marks percentage 0?

Enter marks received in 3 subjects: 45 65 76 
0

What I have tried:

C

//function for the percentage of marks
int marks_percentage (int a, int b, int c)
{
    int sum, percentage, total_marks;
    sum = a+b+c;
    total_marks = 300;
    percentage = sum/total_marks*100;
}

int main()
{
    int a, b, c, mp;
    printf ("Enter marks received in 3 subjects: ");
    scanf ("%d %d %d", &a, &b, &c);
    
    mp = marks_percentage (a,b,c);
    printf ("%d" , mp);
}

Posted 28-Mar-21 1:38am

muquitarif

Updated 28-Mar-21 7:30am

KarstenK

v3

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3 solutions

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Tony Hill · Accepted Answer · 2021-03-28T01:43:00

Solution 1

It is because you are working with integers.

Because the sum (186) is being divided by 300 you end up with 0.62 which cannot be represented as an integer and therefore the answer is 0.

Try the following

percentage = sum * 100/total_marks;

Posted 28-Mar-21 1:43am

Tony Hill

Comments

Tony Hill 28-Mar-21 7:52am

Well spotted Patrice T, I knew the maths was wrong but did not spot the lack of a return.

Patrice T 28-Mar-21 8:07am

My 5, good catch too.

Patrice T · Accepted Answer · 2021-03-28T01:50:00

Solution 2

Quote:
Why my function not working?

try to return a value from the function:

C++

int marks_percentage (int a, int b, int c)
{
    int sum, percentage, total_marks;
    sum = a+b+c;
    total_marks = 300;
    percentage = sum/total_marks*100;
    return ...
}

Posted 28-Mar-21 1:50am

Patrice T

Richard MacCutchan · Accepted Answer · 2021-03-28T01:55:00

Solution 3

Apart from the issue that Tony Hill notes above, you are not returning the percentage value to the caller. So you need the following:

C++

int marks_percentage (int a, int b, int c)
{
    int sum, percentage, total_marks;
    sum = a + b + c;
    total_marks = 300;
    percentage = sum * 100 / total_marks;

    return percentage; // you need to return the calculated value.
}

Posted 28-Mar-21 1:55am

Richard MacCutchan

Comments

KarstenK 28-Mar-21 13:32pm

I prefer using braces when dividing integers to make the compiler really clear what the result should be.
percentage = (sum * 100) / total_marks;

Richard MacCutchan 28-Mar-21 14:04pm

Me too if it is possible to mis-interpret the intent. But in a simple sum like this I do not think it is necessary.