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1.6 Exponentials and logarithms

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Question 21

The temperature of water in a kettle is modelled using the equation $T = 75e^{-kt} + 25$

a.

Explain what the 25 represents in the equation $T = 75e^{-kt} + 25$

[1]

b.

When the kettle is turned off the rate of decrease of the water temperature is $20∘C20^{\circ}\text{C}$ per minute. Find the value of $k$

[3]

c.

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

[3]

Markscheme

1.6 Exponentials and logarithms Questions

A Level
Maths
1.6 Exponentials and logarithms

104 exam-style questions on WJEC A Level Maths 1.6 Exponentials and logarithms, covering 1.6.1 Exponentials and logarithms, 1.6.2 Exponentials and logarithms, 1.6.3 Exponentials and logarithms, 1.6.4 Exponentials and logarithms, 1.6.5 Exponentials and logarithms, 1.6.6 Exponentials and logarithms, 1.6.7 Exponentials and logarithms, 1.6.8 Exponentials and logarithms, and 1.6.9 Exponentials and logarithms. Each one has a worked solution and a mark scheme showing where the marks go.

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