Geometric series

Lessons

1. Geometric series formula:${s_n} = \frac{{{t_1}\;\left( {{r^n} - 1} \right)}}{{r - 1}}$
   Determine the sum of the first twelve terms of the geometric series: 5 – 10 + 20 – 40 + … .
2. Geometric series formula: $s_{n}=\frac{r \cdot t_{n}-t_{1}}{r-1}$
   Determine the sum of the geometric series: 8 + 2 + $\frac{1}{2}$ + …. + $\frac{1}{{512}}$ .
3. A tennis ball is dropped from the top of a building 15 m high. Each time the ball hits the ground, it bounces back to only 60% of its previous height. What is the total vertical distance the ball has travelled when it hits the ground for the fifth time?