To what value does the sum 20+12+36/5---tend as n.
Even though with only 3 terms,
20 + 12 + 36/5 + ....
seems to be the sum of an infinite series with
a = 20 and r = .6
Sum(all terms) = a/(1-r)
= 20/(1-.6)
= 20/.4
= 50
btw, " ---tend as n"
makes no sense.