Answer:
2/5
Step-by-step explanation:
Average is the ratio of the sum of the data to the sample size
Sum of data = 2/5-4/5+9/5/+1/5
Sum of data = (2-4+9+1)/5
Sum of data = 8/5
Sample size = 4
Average = 8/5÷4
Average = 8/5× 1/4
Average = 2/5
Hence the average monthly change in water level is 2/5
