Question 751737
Perimeter of first triangle: 30 cm
second triangle: 15 cm
third triangle: 7.5 cm
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nth triangle: {{{30(0.5)^(n - 1)}}}
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The sum of an infinite geometric series with first term {{{a[1]}}} and common ratio r is {{{a[1]/(1 - r)}}} provided |r| < 1. 
{{{sum(30(0.5)^(n - 1), n= 1, infinity)}}} = {{{30/(1 - 0.5)}}} = {{{highlight(60)}}} cm.