基礎數學問題 20點

1.the population of a city at present is 700 million. the population p,in million,after n years is approximated by the formula p=700e^0.025n

(a)predict the population, in million,after 10 years.
(b)in how many years the population will be doubled?


2>the value of a machine depreciates continuously.after is has used for n years,it's value $v is given by v=Ae^-0.4t,where A is a constant. A new machine is worth
$10000.
(a)find the value of A
(b)find the value of the machine after is has been used for 2 years.
(c)how many years later the value of the new machine reduces to 20% of its original value?

3.the value $V of a famous painting t years after the beginning of 2007 is given by
V=40000(1.5)^0.2t . find the value of the painting at the end of 2012.
(give your answers correct to the nearest integer.)

4.annie deposits $20000 in a bank at 2%p.a. compounded half-yearly.at least
how many years does it take for her to receive an amount exceeding $25000?