# Geometric Sequences

#### JiminPark

How many terms of the geometric sequence 1.2, 2.4, 4.8, 9.6, 19.2...are required for the sum to be greater than 10,000?

Do you use the equation sn=a(1-r^n)/1-r? And how is logarithms included in this question?

#### Plato

MHF Helper
How many terms of the geometric sequence 1.2, 2.4, 4.8, 9.6, 19.2...are required for the sum to be greater than 10,000?
Do you use the equation sn=a(1-r^n)/1-r? And how is logarithms included in this question?
Hint: use $$\displaystyle \log_{10}$$ because $$\displaystyle {S_n} > 10^5$$ .
You want $$\displaystyle S_n> 10^4= 10,000$$.