In a science experiment a substance is decaying exponentially. Its mass, M grams, at time t minutes is given by M= 300e^-0. 5t
The initial mass is found by putting t=0 into the given equation, so the initial mass is 300g. When the mass has decreased to half its value, M=150g. This gives us 150=300e^-0.05t, so e^-0.05t=1/2. Natural log of both sides and re-arranging for t gives t=-ln(1/2)/0.05=13.9 minutes.
TT
Related Maths A Level answers
All answers ▸Use integration by parts to find ∫ (x^2)sin(x) dx. (A good example of having to use the by parts formula twice.)
The equation (k+3)x^2 + 6x + k =5 has two distinct real solutions for x. Prove that k^2-2k-24<0
Solve the differential equation dx/dt=-6*x , given when t=0 x=7.
Solve $\color{orange}{a}x^2 - \color{blue}{b}x + \color{green}{c} = 0$