In first table, where the height of the water is considered, every minute the water rises by 3 cm.
In second table, where possible outcome is considered, for increase in one coin the outcome increases by a factor of two.
The first table, where the height of the water is considered, shows common difference. As it increases equally every minute.
The second table, where possible outcome is considered,shows a common factor as all the values are divisible by 2. So the common factor is 2.