Since the remainder of the questions just involve addition and subtraction I expect that is what is expected here. The farmer can harvest 150 acres each day so
|End of the day
150 + 150 = 300
300 + 150 = 450
Continue that table until he has harvested all 1000 acres.
You could also solve this problem using division. 1000/150 is 6 and 2/3 days. The table method won't give the fraction but it will show your daughter that it takes more than 6 days and less than 7.