Spilled Juice (Missing digit) problems

The video below is only first (Part-1) of the Four videos. It captures the process that the two students (of classes-3 and 4) go through while solving the following problems posed to them:

Students were shown the above image and were asked to solve these problems. No time limit was set. But they took around 20 minutes to solve these 6 problems. They were also allowed to discuss among themselves in case they wanted to.... 

To check all the four videos of this problem, click on this link:
https://www.youtube.com/playlist?list=PLZBBZFls_2nEffHLet8RjYnfTPwGTYXrI

Thanks and Regards
Rupesh Gesota