Simple math. To grow from N to N+1 you need 20+N*2 food. That is, to grow from 2 to 3 you need 24 food, from 3 to 4 - 26 food. With Granary these figures are halved.Araqiel said:I'd also like to mention that your assertion of 2.2:1 hammers to food ratio is wrong.
That is 12 + 13 (=25) food for 60 hammers (cost of 2 pops). 60/25 = 2.4, without any tricks with exchanging 1 pop for 60 hammers.
When your pop is down after whip, set to max food from farms and cottages. If the city hits happiness cap before 10-turn penalty period is expired, switch from farms to cottages only. You lose little or no commerce this way.
Moreover, if you whip units / city improvements as well, you can ignore mines completely and work cottages and a few farms only.