1.5 Exponentials and logarithms

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]

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]

1.5 Exponentials and logarithms Questions