To find the total change in the water level of Marra's pool after 30 days, we will multiply the daily change (which is a decrease of 1/2 inch) by the number of days (30).
The equation for the total change in water level (in inches) after 30 days can be expressed as:
Substituting in the values we have:
So, the equation that shows the approximate total change, in inches, to the water level in her pool after 30 summer days is:
Calculating this gives:
Thus, the water level in Marra’s pool decreases by approximately 15 inches after 30 days.