# What is this kind of sequence called?

I teach English as a second language. In my kids' classes, I sometimes have competitions in order to motivate my students. For one competition, I'm planning on offering monetary prizes: KRW 1,000 for first place, KRW 100 for second place, and KRW 10 for third place.

What is this kind of sequence called? I'm thinking it's logarithmic, but I'm not sure. It's been a long time since I've studied any kind of math.

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Geometric series is a series in which the ratio of the consecutive terms is kept constant. In your example, every term is one-tenth of the previous term, so this constant is $\frac{1}{10}$. You can say that the prize money decreases geometrically. –  Srivatsan Dec 14 '11 at 10:07

It's called a geometric series. Here the ratio of successive terms is constant ie., $\dfrac{t_{n+1}}{t_n} =$ constant $\dfrac{100}{1000} = \dfrac{10}{100} = \dfrac{1}{10}$. This ratio is called the Common Ratio of the Geometric Series.