Question 7628
So the A-final will be 40 grams, right, and you want to know how much you started with 3 days ago? Let's see:


{{{ 40 = A[0]e^(-0.18(3)) }}}


{{{ 40 = A[0]e^(-0.54) }}} <---- simplified.


{{{ (40/e^(-0.54)) = A[0] }}} <---- divide both sides by {{{ e^(-0.54) }}}.


{{{ 68.64 = A[0] }}} <---- Calculate using calculator. You should get approximately 68.64 grams three days ago.


Calculators differ a lot when it comes to how to punch buttons to compute "e to the something" power, so I can't really explain this part to you.