Class 10 Optional Mathematics | The Sum of n Terms of a Geometric Series

Optional Maths, Class 10 · Sequence and Series

The Sum of n Terms of a Geometric Series

Derive the formula · Use it both ways · Find a, r and n

By the end of this lesson you can

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Derive the formula for the sum of n terms

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Choose the form for r < 1 or r > 1

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Find a sum from the last term

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Find a, r or n from a given sum

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5 + 15 + 45 + 135 + 405 + 1215 = 1820. Now try it with twenty terms.

The notes are free to read in full.

Presenter notes: Today we find a quick way to add the terms of a geometric series, however many there are.