Question

What is a possible value for the missing term of the geometric sequences?

1250,___,50,..
A)1200
B)650
C)250
D)125

Answer 1

The answer is:

C) 250

Answer 2

a(n)=ar^(n-1) and we can find the rate upon using the ratio of two points...

50/1250=1250r^2/1250r^0

1/25=r^2

r=1/5 so

a(n)=1250(1/5)^1=250

...

You could have also found the geometric mean which is actually quite efficient too...

The geometric mean is equal to the product of a set of elements raised to the 1/n the power where n is the number of multiplicands...in this case:

gm=(1250*50)^(1/2)=250