how do i work out that if a machine is worth $15000 and if it's price decreases by 20% per annum that it will cost $9600 in two years using

Sn=a(r^n-1)/r-1?

 

using this formula it doesn't work....

thanks guys

$15000 * 0.8^2

 

0.8 is a loss of 20% as a decimal... squared (^2) because its for two years.

how do i work out that if a machine is worth $15000 and if it's price decreases by 20% per annum that it will cost $9600 in two years using

Sn=a(r^n-1)/r-1?

 

using this formula it doesn't work....

thanks guys

 

That formula is for the SUM of a geometric series, not to find any individual term.

 

Using the same notation (a as initial value, r as ratio and n as number of terms), the equation to find the term is ar^n.