Probably want a `to_i` here:

```irb
irb(main):001:0> "1" + 1
TypeError: can't convert Fixnum into String
	from (irb):1:in `+'
	from (irb):1
	from /Users/schisamo/.rbenv/versions/1.9.3-p385/bin/irb:12:in `<main>'
irb(main):002:0> "1".to_i + 1
=> 2
irb(main):003:0> 1.to_i + 1
=> 2
```