Question

What is the common ratio of this geometric sequence?
1|80
2|40
3|20
4|10
5|5
A. -40
B. 0.5
C. 2
D. 40

Answer 1

do you know what the common ratio of a geometric sequence is?

Answer 2

no clue! sorry

Answer 3

hmm. you know what a geometric sequence is, right?

Answer 4

yeah i think so! I'm really bad at math. I am studying for a test!

Answer 5

when you multiply a term consecutively by some number to get the next one, that sequence is a geometric sequence. for example, 2, 4, 8, 16, 32 is a geometric sequence as you multiply each term by 2 to get the next.

Answer 6

oh yeah ok! cool!

Answer 7

to find the common ratio, divide the second term by the first term

Answer 8

the number that you keep multiplying is the common ratio

Answer 9

80, 40, 20, 10, 5

In the above, what is the particular number that you keep multiplying?

Answer 10

is it 2?

Answer 11

because 5*2 is 10, and 10*2 is 20, and so on and so on!

Answer 12

is that right?

Answer 13

Yes

Answer 14

well, you are looking at this in reverse. what do you multiply 80 to for getting 40?

Answer 15

divide the second term by the first term.....40/80 = common ratio

Answer 16

you don't multiply you divide.

Answer 17

so its 0.5

Answer 18

what do you multiply 80 to for getting 40? 0.5

Answer 19

it is the same thing.

Answer 20

no...in a geometric sequence you multiply to find the next term. However, to find the common ratio, you divide the second term by the first term

Answer 21

Wait what? im confused now!

Answer 22

but its B right? 0.5

Answer 23

all right... just memorize that way: 2nd term/1st term

Answer 24

I am sorry PathKohli....I did not mean to confuse kcurri....I should not have stepped in on this one

Answer 25

nah! no problem.

Answer 26

Thanks @ParthKohli and @texaschic101

Answer 27

read this kcurri...maybe it will help
http://www.regentsprep.org/Regents/math/algtrig/ATP2/GeoSeq.htm

Answer 28

anytime :)

Answer 29

okay