If 7 balls, determine which is lightest in the least amount of weighs.

ball_weight.rb

ball1, ball2, ball3, ball4, ball5, ball6, ball7 = 2.7, 2.5, 2.7, 2.7, 2.7, 2.7, 2.7
group1 = [ball1, ball2, ball3]
group2 = [ball4, ball5, ball6]

if group1.inject(:+) == group2.inject(:+)
    puts "Ball 7 is the lightest."
elsif group1.inject(:+) < group2.inject(:+)
    case group1[0] <=> group1[1]
        when 0
            puts "Ball 3 is the lightest."
        when 1
            puts "Ball 2 is the lightest."
        when -1
            puts "Ball 1 is the lightest."
    end
elsif group2.inject(:+) < group1.inject(:+)
    case group2[0] <=> group2[1]
        when 0
            puts "Ball 6 is the lightest."
        when 1
            puts "Ball 5 is the lightest."
        when -1
            puts "Ball 4 is the lightest."
    end
end