Last week, a farmer shipped 10 boxes of pomelos which had 240 pomelos in all. This week, the farmer shipped 20 boxes. How many dozens of pomelos did the farmer ship in all? Let's think first. Chain of thought:
There were 240 / 10 = 24 pomelos in a box. This means that each box has 24 / 12 = 2 dozens of pomelos since 1 dozen is equal to 12. The farmer shipped a total of 10 + 20 = 30 boxes. Thus, the farmer shipped a total of 30 x 2 = 60 dozens of pomelos.
Therefore, the answer is 60.