Engineering maths problem

mFBk SG

Hi... i need some help on engineering maths problem.. Hope someone can help me to find a solution to it... Tried to solve but cant...

Here is the question :

A certain radioactive material is known to decay at a rate proportional to the amount present. There are 200mg of the material present initially. After 5 hours, it is observed the material has lost 10% of the original mass. Let m denote the mass of the material remaining at the time, t.

(a) Write down the differential equation which describes the rate of change of m with respect to t?

(b) Solve the differential equation.

(d) How long will it take for the material to decay to half its original mass?

deepak.c SG

I hope this helps, it's similar.

http://www.sgforums.com/forums/2297/topics/362727

Deadstroke SG

I am assuming you know your stuff, so skip some steps.

1. dM/dt = kt

2. Solve the above, M = Aexp(kt), A and k are constants

3. plug in inital and t=5 values to solve for A and k