title: How to find the sum of factorials
body: <p>Using minitest, I'm trying to make this test pass, which is asking for the sum of <code>5!</code>:</p>
  
  <pre><code>def test_sum_of_factorials
  
    sum_of_factorials = 0
    numbers = [1, 2, 3, 4, 5]
  
  
    assert_equal 153, sum_of_factorials
  end
  </code></pre>
  
  <p>I wrote a passing solution but it is long and repetitive: </p>
  
  <pre><code>fractorial_5 = numbers.inject(1) {|aggregate, num| aggregate * num}
  fractorial_4 = numbers[0..3].inject(1) {|aggregate, num| aggregate * num}
  fractorial_3 = numbers[0..2].inject(1) {|aggregate, num| aggregate * num}
  fractorial_2 = numbers[0..1].inject(1) {|aggregate, num| aggregate * num}
  fractorial_1 = 1
  
  fractorials_array = [fractorial_1, fractorial_2, fractorial_3, fractorial_4, fractorial_5]
  
  fractorials_array.each {|fractorial| sum_of_factorials += fractorial}
  </code></pre>
  
  <p>Does anyone have a cleaner, simpler solution that they'd be willing to explain? </p>