nthPrimeNumber.rb

def get_range(max)
    range = [0, 0, 2]
    (3..max).each do |num|
        num.odd? ? (range << num) : (range << 0)
    end
    range
end

def sum_of_primes(max)
    range = get_range(max)
    i = range[3]
    while true
        (i*i).step(max, i) do |num|
            range[num] = 0
        end

        i = range.find{|item| (item > i)}
        break if i*i > range.length
    end
    range.inject(:+)
end