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1.5 Exponentials and logarithms

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Question 6
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The temperature of water in a kettle is modelled using the formula T=75e−kt+22T = 75e^{-kt} + 22T=75e−kt+22 Where T T\,T is the temperature t t\,t minutes after the kettle is turned off and k k\,k is a positive constant.

a.

Find the rate of change of the temperature in terms of kkk

[2]
b.

After 5 minutes the temperature of the water is 70∘C70^{\circ}\text{C}70∘C. Find the value of kkk

[3]
c.

Find how many minutes it takes for the water to cool to 55∘C55^{\circ}\text{C}55∘C

[4]

1.5 Exponentials and logarithms Questions

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