He then went to see the oranges being harvested. He found out that they harvest 46 sacks per day and discard 21 of them. How many oranges do they harvest per day if each sack contains 40 oranges?
1. He sees 46 sacks being harvested per day. 
2. He sees that 21 of those sacks are discarded. 
3. He knows that each sack contains 40 oranges. 

We want to find out how many oranges are harvested per day. 

Step 1: 46 sacks are harvested per day. 
Step 2: 21 of those sacks are discarded. 
Step 3: 46 - 21 = 25 sacks are not discarded. 
Step 4: 25 sacks x 40 oranges per sack = 1,000 oranges are harvested per day.