Question

Find the 15th term in the geometric sequence below.

20, 10, 5, 2.5, . . .
A.-25/4,096

B.-5/4,096

C.5/4,096

D.25/4,096

Answer 1

geo sequence

`a_n=a_1r^(n-1)`
an=nth term
a1=first term
r=common ratio
n=which term

10/20=1/2
r=1/2
20=a1


`a_(15)=20(1/2)^(15-1)`=

`a_(15)=20(1/2)^(14)`=

`a_(15)=20( (1)/(16384) )`=

`a_(15)= (20)/(16384)`=

`a_(15)= (5)/(4096)`




C is answer