select 
  grade, 
  decode(grade, 'E', '33-39',
                'D', '40-49',
		'C', '50-59',
		'B', '60-69',
		'A', '70-79',
		'A+','80% and above'
        ) pct,
  count(*) no_of_students
from your_table
group by   
  grade, 
  decode(grade, 'E', '33-39',
                'D', '40-49',
		'C', '50-59',
		'B', '60-69',
		'A', '70-79',
		'A+','80% and above'
        );