Dennis bought a surfboard originally priced at $75 but on sale for 20% off. After 10% sales tax, what was the total cost?
2 answers:
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Answer:
- k ≈ 0.060
- T(4) ≈ 178 °F
Step-by-step explanation:
The desired formula parameters for Newton's Law of Cooling can be found from the given data. Then the completed formula can be used to find the temperature at the specified time.
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<h3>Given:</h3>
k
T(4)
<h3>Solution:</h3>Filling in the given numbers, we have ...
185 = 68 +(208 -68)e^(-k·3)
117/140 = e^(-3k) . . . . . subtract 68, divide by 140
ln(117/140) = -3k . . . . . . take natural logarithms
k = ln(117/140)/-3 ≈ 0.060
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The temperature after 4 minutes is about ...
T(4) = 68 +140e^(-0.060·4) ≈ 68 +140·0.787186
T(4) ≈ 178.205
After 4 minutes, the final temperature is about 178 °F.
