Geometric sequence question? (1 Viewer)

[countrydude]

Hi I am doing some maths study today and this question is annoying me so could someone do it for me please? (im such a dumass at maths)

Which term of the sequence 3,6,12... is equal to 384?

I am having trouble at the end part, i suck at equation stuff to....

thanks

 

[abdooooo!!!]

r = T2/T1 = 2

Tn = ar^n-1
384 = 3 x 2^n-1
128 = 2^n-1
ln128/ln2 = n-1
n - 1 = 7
n = 8

therefore 384 it is the 8th term.