CSS CSS Basics Basic Layout Floats

In 1st float video, the image columns collapse, however if you only set float: right to .resort, it will appear fine????

1 ) In the video, when the instructor perform the following task:

.tip { float: right; }

.resort { float: left }

the layout collapse and the footer goes to the top fo the image

2 ) However, I realized that if you just set .resort { float: right; }

The layout will not collapse, and it will appear fine!

So my question is: why should we choose to do it by '1)' 's way and then add more code to fix the layout when there is a easier way to fix the problem '2)'??