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A mountain gorilla weighs 135 pounds and is gaining 0.5 pounds per week. An Eastern gorilla weighs 141 pounds and is losing 0.25 pounds per week.

Which of the following equations could be used to determine the number of weeks that it will take until the gorillas weigh the same amount?

A. [tex]135 + 0.5w = 141 + 0.25w[/tex]
B. [tex]135 + 0.5w = 141 - 0.25w[/tex]
C. [tex]135w + 0.5 = 141w + 0.25[/tex]
D. [tex]135 - 0.5w = 141 + 0.25w[/tex]

Answer :

Sure, let's solve the problem step-by-step:

1. Identify the Initial Weights and Rate of Change:
- The mountain gorilla initially weighs 135 pounds and gains 0.5 pounds per week.
- The Eastern gorilla initially weighs 141 pounds and loses 0.25 pounds per week.

2. Set Up an Equation to Represent Each Gorilla's Weight Over Time:
- For the mountain gorilla: Its weight over time can be represented as [tex]\(135 + 0.5w\)[/tex], where [tex]\(w\)[/tex] is the number of weeks.
- For the Eastern gorilla: Its weight over time can be represented as [tex]\(141 - 0.25w\)[/tex].

3. Determine When Their Weights are Equal:
- We need to find the number of weeks [tex]\(w\)[/tex] when both gorillas weigh the same. This means we set their weight expressions equal to each other:
[tex]\[
135 + 0.5w = 141 - 0.25w
\][/tex]

4. Formulate the Equation:
- Looking at the options provided:

A. [tex]\(135 + 0.5w = 141 + 0.25w\)[/tex] (Incorrect, because the Eastern gorilla is losing weight, not gaining.)

B. [tex]\(135 + 0.5w = 141 - 0.25w\)[/tex] (Correct, matches the situation described.)

C. [tex]\(135w + 0.5 = 141w + 0.25\)[/tex] (Incorrect form of the equation.)

D. [tex]\(135 - 0.5w = 141 + 0.25w\)[/tex] (Incorrect, as it does not represent the description given.)

5. Correct Equation:
- The correct equation to use is option B: [tex]\(135 + 0.5w = 141 - 0.25w\)[/tex].

This equation can be used to solve for [tex]\(w\)[/tex], which represents the number of weeks until the gorillas weigh the same amount.

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