<PRE><B>Question 1034059</B>
Well, the situation describes the series
100 + 200 + 300 + 400 + ...where the total is the overall height of the airplane...we want to know when this total exceeds 12000...
Such an arithmetic series and sum can be described mathematically as
{{{S[n] = (n/2)(2a[1] + (n-1)d)}}}
Now plug in to get
{{{12000 = (n/2)(2*100 + (n-1)(100))}}}
{{{12000 = (n/2)(200 + 100n - 100)}}}
{{{12000 = (n/2)(100n + 100)}}}
Continue solving for n...
{{{12000 = 50n(n + 1)}}}
{{{240 = n(n+1)}}}
{{{n^2 + n - 240 = 0}}}
{{{(n+16)(n-15) = 0}}}
n = 15
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