Program Issue, if and else if statements

For some reason everytime i run my program the answer is always B. Im not sure why this is, please help!

Code:

    //Figure out letter grade
    if (the_student.percentTotal>= 90)
    {
        the_student.letterGrade = 'A';                           
    }
    else if ((the_student.percentTotal>= 80) || (the_student.percentTotal < 90))
    {
         the_student.letterGrade = 'B';
    }
    else if ((the_student.percentTotal>= 70) || (the_student.percentTotal < 80))
    {
         the_student.letterGrade = 'C';
    }
    else if ((the_student.percentTotal>= 60) || (the_student.percentTotal < 70))
    {
         the_student.letterGrade = 'D';
    }
    else if (the_student.percentTotal<60)
    {
         the_student.letterGrade = 'F';
    }

Can you come up with a number, call it percentTotal, where the if before the "B" clause is false? (Hint: No.) (Double hint: || does not mean "and".)

In addition, if you have established that n >= 90 is not true (the first condition is false), there is no point checking in the else block if n is smaller than 90. You wouldn't have got to the else block if it wasn't so.
Similarly for all comparisons down the chain.