Population type problems are also easily dealt with in this way.
For example, “A population of mice numbers 5600 and is growing at a rate of 12.5% per
month. How long will it be until it numbers more than one million?”
Pressing
CLEAR
(above
DEL
) clears out the existing expressions, and
we can enter the formula for the GP modeling the situation shown right.
Because this is a non-recursive rule, the two initial values of 5600 and
6300 will be automatically calculated when you enter the rule into
U1(N)
.
All we need do now is switch to the Numeric view to find, with some
experimenting, that
U1(46)
is the first to exceed one million.
It is also possible to answer these questions in the Solve aplet. For
example if we use the Sequence aplet to define
U1(N)=2^(N-1)
as
before, then we can change to the Solve aplet and enter into
E1
the
equation
U1(N)=10000
, change to the
NUM
view and press
and obtain an answer of
14 29
. This means, of course that
N=15
is
⋅
the first term exceeding 10000.
The reason why we did not use
E1(N)>10000
is that the Solve aplet is unable to deal with inequalities even
though no error message is given if you try.
103