Task-5.1.c

#include <stdio.h>

void main()
{
    float marks1, marks2, marks3, average;

    printf("Enter marks obtained in subject 1 :");
    scanf("%f", &marks1);
    printf("Enter marks obtained in subject 2 :");
    scanf("%f", &marks2);
    printf("Enter marks obtained in subject 3 :");
    scanf("%f", &marks3);

    average = (marks1 + marks2 + marks3) / 3;
    printf("Average : %0.2f\n", average);

    if (average >= 90)
    {
        printf("Grade A");
    }
    else if (average >= 80)
    {
        printf("Grade B");
    }
    else if (average >= 70)
    {
        printf("Grade C");
    }
    else if (average >= 60)
    {
        printf("Grade D");
    }
    else
    {
        printf("Grade F");
    }
}