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OG 12 #98

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OG 12 #98

by jimmynicho » Fri Jun 19, 2009 1:37 pm
On a scale that measures the intensity of a certain phenomen, a reading of n+1 corresponds to an intensity that is 10 times the intensity corresponding to a reading of 8 is how many times as great as the intensity corresponding to a reading of three?
a)5
b)50
c)10^5
d)5^10
e)8^10-3^10
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by vasbli » Fri Jun 19, 2009 1:49 pm
first lets get the question right:

On a scale that measures the intensity of a certain phenomen, a reading of n+1 corresponds to an intensity that is 10 times the intensity corresponding to a reading of n.

8 is how many times as great as the intensity corresponding to a reading of three?

Again, GP question, with n+1=10n. hence, n=10(n-1), and by combining
n+1=10x10(n-1)=10^2(n-1)

the 8th term of the GP is 10^5 the 3rd term
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by ssmiles08 » Fri Jun 19, 2009 2:14 pm
You can also do this by the counting method since the numbers 3 and 8 arent that far apart.

let 3 have an intensity of i.

3 = i
4 = 10*i
5 = 100*i
6 = 1000*i
7 = 10^4*i
8 = 10^5*i

therefore the intensity of 8 is 10^5 times greater than 3

(C)
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