He then went to see the oranges being harvested. He found out that the harvest will go on for 15 days. How many sacks do they harvest per day if they harvested a total of 30 sacks of oranges?
1. He went to see the oranges being harvested. 
2. He found out that the harvest will go on for 15 days. 
3. They harvested a total of 30 sacks of oranges. 

This is a word problem, so we need to read it carefully and identify what information we are given, and what we need to find. In this case, we are given the total number of sacks harvested, and the number of days of the harvest, and we need to find the number of sacks harvested per day. 

We can set up a proportion to solve this problem: 

$$\frac{30}{15} = \frac{x}{1}$$

Cross-multiplying, we get: 

$$30 = 15x$$

$$x = 2$$

So, they harvest 2 sacks of oranges per day.