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@score=[]
@balance=[]
sum=0
total_credit=0
puts "input your the number of your courses:"
course_number=gets
puts "inputs your scores now:"
for i in 1..course_number.to_i
  temp=gets
  @score<<temp.to_i
end
puts "input your balance now:"
for i in 1..course_number.to_i
  temp2=gets
  @balance<<temp2.to_i
end
for i in 1..course_number.to_i
  sum=sum+@score[i].to_i*@balance[i].to_i
end
for i in 1..course_number.to_i
  total_credit=total_credit+@balance[i].to_i
end
result=sum/total_credit
puts "your balance average score is #{result}"