Why does the div get out of the general block?

Question

css

https://jsfiddle.net/16jfut8z/1/
Block width - 100%
inside it are two divs with width 65 + 35 = 100%
why are they not side by side?

Answer 1

https://jsfiddle.net/16jfut8z/5/
Because you didn't set the streamlining.