Set 4: Exponential Functions

Explanation

Answer: B

The temperature difference decreases by 10% every minute. If it starts at 50 degrees, what is the equation?

$Temperature Decay$

$D(t) = 50(0.10)^t$

$D(t) = 50(0.90)^t$

✓ Correct

$D(t) = 50 - 10t$

$D(t) = 50(1.10)^t$

Detailed Explanation

Choice B is correct. Choice B is the correct answer. Decrease of 10% means 90% remains. 1. Identify Rate: $r = 0.10$ . 2. Calculate Factor: $b = 1 - 0.10 = 0.90$ . 3. Equation: $D(t) = 50(0.90)^t$ . Strategic Tip: Always use what remains for the base. Choice A is incorrect because 0.10 means losing 90%. Choice C is incorrect because it is linear.

Key Steps:

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The correct answer is $D(t) = 50(0.90)^t$

Why others are wrong:

A: Choice A 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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