a particle moving horizontally in a straight line experiences retardation of kv m/s^2 where v is its velocity. the initial velocity is 150 m/s and is reduced to 50 m/s in a time of 1 second. it travels a distance s m in this time.

(i) find the value of k

(ii)deduce an expression for the velocity at any time t.

(iii) show s=100/ln3 m

I was able to work out part (i) by letting dv/dt =-kv i then integrated this and put in the limits I was given in the question and I got an answer of k=ln3

I am stuck on part (ii) . I have tried letting dv/dt =(ln3)v . I then integrated this and put in the limits of initial velocity 150 and final of v . I got v=ln150-ln3t. this is not the right answer. the right answer is v=150e^-(ln3)t m/s