?? - 2015 q4 Answers
(a) Water is being heated in an electric kettle. The temperature, θ°C, of the water t seconds after the kettle is switched on, is modelled by the equation
θ = 120 - 100eλt, 0 ≤ t ≤ T
State the value of θ when t = 0 (1)
Given that the temperature of the water in the kettle is 70°C when t = 40,
b) find the exact value of λ, giving your answer in the form lna/b, where a and b are integers (4)
When t = T, the temperature of the water reaches 100°C and the kettle switches off.
(c) Calculate the value of T to the nearest whole number. (2)
State the value of θ when t = 0 (1)
Given that the temperature of the water in the kettle is 70°C when t = 40,
b) find the exact value of λ, giving your answer in the form lna/b, where a and b are integers (4)
When t = T, the temperature of the water reaches 100°C and the kettle switches off.
(c) Calculate the value of T to the nearest whole number. (2)