Thursday

August 27, 2015
Posted by **SHERYL** on Thursday, March 31, 2011 at 8:12am.

16,40,100,?,?

IS there a common ratio for the geometric sequence and what are the missing terms?

81,54,?,?,?

- math -
**drwls**, Thursday, March 31, 2011 at 9:42amYes, and 2.5 is the ratio. Following terms are 150, and 225.

For the second question, try 2/3 for the ratio. 36, 24, ...

With only two terms, one really can't say if there is a "common" ratio. There are no other pairs to compare.

- math -
**Jai**, Thursday, March 31, 2011 at 10:18amif the given sequence is a geometric sequence, then it follows the formula

A,n+1 = r*(A,n)

where

r = ratio between two consecutive terms

A,n = the nth term

A,n+1 = the term after A,n

substituting the first and second term,

40 = r*16

r = 40/16

r = 2.5

to check, let's see if we would obtain 100 if we multiply 40 by the ratio=2.5

40*2.5 = 100

to find the next term after 100, we just multiply by the ratio,, thus the next two terms are:

100*2.5 = 250

250*2.5 = 625

for the second question, if it's a geometric sequence, then it follows the formula above. thus, getting the ratio,

54 = r*81

r = 54/81

r = 2/3

to get the next three terms, we multiply the next terms by 2/3:

54*(2/3) = 36

36*(2/3) = 24

24*(2/3) = 16

hope this helps~ :)