<PRE><B>Question 1017338</B>
Find sum of first 100 terms of an arithmetic 
sequence with 15th term of 86 and first term of 2. 
&lt;pre&gt;&lt;b&gt;
a&lt;sub&gt;n&lt;/sub&gt; = a&lt;sub&gt;1&lt;/sub&gt; + (n-1)d

86 = 2 + (15-1)d

84 = 14d

{{{84/14}}} = d 

6 = d

S&lt;sub&gt;n&lt;/sub&gt; = {{{n/2}}}[2a&lt;sub&gt;1&lt;/sub&gt; + (n-1)d] 


S&lt;sub&gt;100&lt;/sub&gt; = {{{100/2}}}[2(2) + (100-1)6]

S&lt;sub&gt;100&lt;/sub&gt; = 50[4 + (99)6]

S&lt;sub&gt;100&lt;/sub&gt; = 50[4 + 594]

S&lt;sub&gt;100&lt;/sub&gt; = 50[598]

S&lt;sub&gt;100&lt;/sub&gt; = 29900

Edwin&lt;/pre&gt;&lt;/b&gt;
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