The mass, m grams, of a radioactive substance t years after it was first measured is modelled by m = 50e-kt. The half-life of the substance is 8 years.
(a) Show that k = (ln 2)/8.
(b) Find the mass after 20 years.
(c) Find the time taken for the mass to fall to 1 gram.
(d) Find the rate at which the mass is decreasing when t = 0.
From Paper 1: Pure Mathematics 1
97 marks
Two variables x and y satisfy y = abx, where a and b are constants. A graph of log10 y against x is a straight line with gradient 0.3 and intercept 1.2 on the vertical axis.
(a) Find the values of a and b, giving your answers to 3 significant figures.
(b) Use the model to estimate y when x = 5.
Score 0 / 15 · 0 of 2 marked
This paper is written by Plasmo in the style of the Edexcel A-Level Maths exam. It is not a past paper and is not produced or endorsed by the exam board.
Exponentials and logarithms Exam Questions: Edexcel A-Level Maths | Plasmo