Problem 74 - Introductory Algebra for College Students

Question

Solve by writing a sum of signed numbers and adding. Lake Assal in Africa is 512 feet below sea level. What is the elevation of a person standing 642 feet above Lake Assal?

Step-by-Step Solution

Answer

The elevation of the person is 130 feet above sea level.

Step 1: Understanding the problem

Firstly, need to understand that the sea level is considered the 0 point. Anything above sea level is positive and anything below sea level is negative. Now, Lake Assal is 512 feet below sea level, so it is -512 feet. The person is standing 642 feet above Lake Assal.

Step 2: Signed Numbers

Since the person is standing above the lake, his position compared to Sea level can be found by a sum of signed numbers. His standing position will be the sum of signed numbers which is (-512) + (+642).

Step 3: Addition

Now just add these values. Note that when adding a negative number, it's like subtracting. -512 + 642 equals 642 - 512. Therefore, the elevation of the person will be 642 - 512 = 130 feet above sea level.