Question

In 4 years, a reef’s elevation fell from 10 mm above sea level to 2 mm below sea level. The expression (-2-10)•4 gives the change in elevation per year. What was the change in elevation in mm per year?

A. 2mm/yr
B. -2mm/yr
C. 3mm/yr
D. -3mm/yr

Answer 1

The change in elevation per year is -3 mm/yr, as the reef's elevation fell by a total of 12 mm over 4 years.

Step-by-step explanation:

The change in elevation per year can be calculated using the expression given in the question, which is (-2 - 10) × 4. This expression factors in the change from 10 mm above sea level to 2 mm below sea level over a period of 4 years.

First, calculate the total change in elevation: -2 mm (final elevation) - 10 mm (initial elevation) = -12 mm. This means the reef's elevation fell by 12 mm over the 4 years.

To find the average change per year, divide the total change by the number of years: -12 mm ÷ 4 years = -3 mm/year. Therefore, the change in elevation in mm per year is -3 mm/yr.