Set 5: Linear Equations (Intermediate)

Explanation

Answer: A

A boat goes 15 mph in still water. The current is 5 mph. How long to go 40 miles upstream?

✓ Correct

Detailed Explanation

Choice A is correct. Choice C is the correct answer. 1. Upstream Speed: $15- 5 = 10$ mph. 2. Equation: $10t = 40$ 3. Divide by 10: $t = 4$ Choice D is incorrect because it results from an error in the solution process. Choice C is incorrect because it results from an error in the solution process. Choice A is incorrect because it results from an error in the solution process.

Key Steps:

•

The correct answer is 4

Why others are wrong:

B: Choice B is incorrect and may result from a calculation error.

C: Choice C is incorrect and may result from a calculation error.

D: Choice D is incorrect and may result from a calculation error.

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