I am not able to complete this loop perfectly - c

Question

write a program to enter five marks and by taking its average percent to determine the grade(only using nested if else) by following conditions:
if 90 and above: grade A
if 80-70: grade B
if 70-80: grade C
if 50-70: grade D
if below 50: fail
I did try the loop starting from backward by using if(avg>=50) but it did not give me the desired output because it will always be stuck at you failed which I kept it in else condition.
if ( avg <= 90 )
{
if ( avg <= 80 )
{
if ( avg <= 70 )
{
if ( avg <= 50 )
{
printf( "Fail" );
}
else
{
printf( "D" );
}
}
else
{
printf( "C" );
}
}
else
{
printf( "B" );
}
}
else
{
printf( "A" );
}
If I enter marks above 90 then I expect the output to come A but instead it comes you have "failed"

Answer 1

You should try using else if ladder
if(avg>=90)
{
printf("A");
}
else if(avg>=80)
{
printf("B");
}
else if(avg>=70)
{
printf("C");
}
else if(avg>=50)
{
printf("D");
}
else{
printf("Fail");
}

Answer 2

This should work:
int main()
{
int marks[5];
int i,j;
float avg;
int total=0;
for(i=0;i<5;i++)
{
scanf("%d",&marks[i]);
}
for(j=0;j<5;j++)
{
total = total+marks[j];
}
avg = total/5;
if(avg<50)
{
printf("Fail");
}
else
{
if(avg>=50 &&avg<70)
{
printf("C");
}
else if(avg>=70)
{
if(avg>=80)
{
if(avg<90)
{
printf("B");
}
else if (avg>=90)
{
printf("A");
}
}
}
}
}

Answer 3

In your case, I think switch statement may be the best solution.
# include <stdio.h>
const char * mark(int grade){
switch (grade/10){
case 10:
case 9:
return "A";
case 8:
return "B";
case 7:
case 6:
case 5:
return "C";
default:
return "Fail";
}
}
int main(int argc, char* argv[]){
int grade;
for(int i = 1; i < argc; ++i){
if (sscanf(argv[i], "%d", &grade) < 1){
fprintf(stderr, "\"%s\" can not be converted to an int.\n", argv[i]);
return -1;
}else{
printf("%s\n", mark(grade));
}
}
return 0;
}