Answer:
70%
Explanation:
Given that:
Initial water level in the tank at noon = 10 cm
After several hours, water level = 3 cm
To find the percentage change in the water in the tank, we can use the following formula:

Here, Final Value = 3 cm
Initial Value = 10 cm
Putting the values in the formula:

Here, negative value, means there is a decrease in the final value from the initial value.
Therefore, the answer is 70% decrease.