Final answer:
The farmer uses 36% of the total area of his land to grow crops.
Step-by-step explanation:
To find the percentage of the total area of his land used to grow crops, we need to first find the fraction of his land that he uses for crops. He uses 1.8 out of every 5 acres of land for crops, so the fraction would be 1.8/5.
To find the percentage, we can multiply this fraction by 100. (1.8/5) * 100 = 36%.
Therefore, the farmer uses 36% of the total area of his land to grow crops.