I am trying to solve a sigma/summation notation problem:

n = 99, i = 4 and each term in the sequence is determined by (1/i) - (1/(i+1)).

Since n = 99, I think it's safe to assume my professor does not want me to actually go through the process of subbing in "i" 99 times to find the answer.

How should I approach this question? Do I evaluate this question as a limit approaching 99? Also does the fact that the "i" is in the denominator of a rational create any extra steps I need to take? Thank you for the help.

3 answers

Note that the series is collapsing. All the terms except the first and the last cancel out!

(1/4 - 1/5) + (1/5 - 1/6) ... + (1/99 - 1/100) = 1/4 - 1/100
Ah! Oh my, I completely missed that! Thank you for the help Steve.
Always be on the lookout for trick questions...

Develop your inner laziness!
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