Check out example codes for "What does inject in ruby do". It will help you in understanding the concepts better.
Code Example 1
[3, 6, 10].inject {|sum, number| sum + number} =>|3, 6| 3 + 6 => 9 =>|9, 10| 9 + 10 =>19
Code Example 2
[3, 6, 10, 13].inject(:+) => (((3 + 6) + 10) + 13) => 32
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