T-SQL DECLARING VARIABLES

Question

declare 
@sid int,@sname varchar(20),@s1 int,@s2 int,@s3 int,@totalmarks int,@avg float,
@grade1 char(1),@grade2 char(1),@grade3 char(1),@percentage float,@actualmarks int
begin 
set @sid=487
set @sname='venkat'
set @s1=100
set @s2=85
set @s3=55
set @totalmarks=@s1+@s2+@s3
set @avg=@totalmarks/3
set @percentage=cast(@totalmarks /(@actualmarks*100) as float
set @grade1='a'
set @grade2='b'
set @grade3='c'
if(@percentage <55)
begin 
print @grade3
end
if(@percentage >=55 or @percentage <=75)
begin 
print @grade2
end
if(@percentage >75)
begin 
print @grade1
end
print @sid
print @sname
print @totalmarks
print @avg
print @percentage
end

I AM UNABLE TO PRINT  PERCENTAGE 

IT IS SHOWING   Must declare the scalar variable "@percentage".

AND I NEED TO PRINT GRADE ALSO BASED ON PERCENTAGE 

I AM UNABLE TO DO IT  PLEASE HELP ME