sample.rb

papers = [80, 10, 20, 30, 71, 69, 100]
result = papers.reduce(
    {passing: [], rejected: [], }
  ) do |boxes, paper|
    if paper >= 70 then boxes[:passing] else boxes[:rejected] end << (paper)
    boxes
  end
p result
# => {:passing=>[80, 71, 100], :rejected=>[10, 20, 30, 69]}