How to multiply (pass) cells using trypsin

This video shows how to pass cells from 1 75cm^2 flask into 3 new flasks in a 1:3 ratio using trypsin. The cells used in the video are ASK cell line (Atlantic Salmon Kidney).
Steps:
1- clean your station and bring everything you need under the hood.
2 - label your new flasks
3 - put fresh media into your new flasks
4- remove old media
5- rinse the old flask with 10ml of room temperature PBS
6- rinse again with 10ml PBS but leave it for 1min.
7- remove the PBS
8- add 5ml of trypsin
9- observe under the microscope until some cells are detached and floating by rocking the flask (should take under 30s.)
10- lift your flask up so the trypsin doesnt touch the remaining cells.
11- remove the trypsin and hit the flask to detach the remaining cells.
12- add 6ml of new media and do 4-5 up and downs to get most cells.
13- take the 6ml and transfer 2ml of it into each new flask
14- check under the microscope to make sure cells are indeed in the flask
15- incubate your cells!