Final answer:
The rate at which the group of workers can plant is 9 acres per day, determined by dividing the total acres (81) by the number of days (9).
Step-by-step explanation:
To find the rate of acres planted per day by a group of workers who can plant 81 acres in 9 days, we simply divide the total number of acres by the total number of days:
Rate = Total Acres / Total Days
Rate = 81 acres / 9 days
Rate = 9 acres per day
Therefore, the workers plant 9 acres of land per day.