We have a proportional relationship: for every 10 minutes outside, we have 20 minutes inside of playing.
Then, if "In" is the number of minutes inside and "Out" is the number of minutes outside, we can write:
The constant of proportionality k can be calculated from the fact that for every 10 minutes outside, we have 20 minutes inside of playing.
This means that when Out=10, In=20, so we have:
Then:
This can be read as "the number of minutes inside is 2 times the number of minutes outside".
Then, we can complete the table:
Minutes outside: 10 20 30 40
Minutes inside: 20 40 60 80