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30 Sep 2004, 12:32
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What is the quickest way to find the value of a certain term in a progression?
For example:
20, 40, 80, 160, 320...
What's the quickest way to find out what the 20th term in that sequence is?
For example:
20, 40, 80, 160, 320...
What's the quickest way to find out what the 20th term in that sequence is?
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Thank you for understanding, and happy exploring!
I cant think of any quicker way other than to use GP (Geometric progression).
If you look at the sequence, you see the numbers doubling OR we can say that the numbers have a common ratio - in this case '2'. The formula is
nth term = a*(r^n-1). a= first term. r= common ratio and n=nth term
The 20th term will be = 20x2^(20-1) = 20x2^19 = 10485760
If you look at the sequence, you see the numbers doubling OR we can say that the numbers have a common ratio - in this case '2'. The formula is
nth term = a*(r^n-1). a= first term. r= common ratio and n=nth term
The 20th term will be = 20x2^(20-1) = 20x2^19 = 10485760
30 Sep 2004, 12:50
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a(r^ (n-1) )
a is the first term , r the common factor, n the number of term ins equence.
a is the first term , r the common factor, n the number of term ins equence.
