Tutorial: Arithmetic and Geometric Progressions

[Anonymous]

Almost a detail, but in the Arithmetic and Geometric Progressions tutorial you write the sum of geometric progression as

a.(1-rⁿ)/(1-r) if r<1

a.(rⁿ-1)/(r-1) if r>1

which is not false, but redundant, right (since this is the same equation in any case) ?

[kzg]

Tutorial: Arithmetic and Geometric Progressions

[Anonymous]

Kzg,

You are right. The formula is the same, but I wanted to stay aligned with the slight distinction PRMIA handbook makes too in cases where r>1 and r<1 - perhaps with a view to avoiding negative numbers in the numerator and denominator. I wonder why though because nearly everyone studying for the PRM can be expected to be comfortable dealing with negative numbers

Mukul

[Author]

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