p,r,s,t,u An arithmetic sequance is a sequence in which each

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p,r,s,t,u An arithmetic sequance is a sequence in which each [#permalink]

13 Apr 2008, 11:02

p,r,s,t,u

An arithmetic sequance is a sequence in which each term after the first is equal to the sum bof the preceding term and a constant. If the list of numbers shown above is an arithmetic sequence, which of the following must also be an arithmetic sequence?

I. 2p, 2r, 2s, 2t,2u
II. p-3, r-3, s-3, t-3, u-3
III. p^2, r^2, s^2, t^2, u^2

a) I only
b) II only
c) III only
d) I and II only
e) II and III only

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Re: sequence [#permalink]

13 Apr 2008, 11:53

B.
AS-arith. sequence.
X- any real number.
AS(1) +/- X = AS(2) (always true).

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Re: sequence [#permalink]

13 Apr 2008, 12:14

can u describe in details plsssssssssssss?

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Re: sequence [#permalink]

13 Apr 2008, 14:03

let the original sequence be written as below by adding the constant each time

p, p+c, p+2c, p+3c, p+4c

lets transform the above as per our choices

I) 2p, 2p+2c, 2p+4c, 2p+6c, 2p+8c (this is an arithmetic seq. since there is an equal increase of 2c in each term of the sequence)
II) p-3, p+c-3, p+2c-3, p+3c -3, p+4c-3 (this is an arithmetic seq, since there is an equal increase of c in each term)
III) p^2, (p+c)^2, (p+3c)^2.... (just looking at the first 3 terms, the increase isn't constant, since in the second term the increase is 2pc+ c^2 and in the third term the increase is 6pc+9c^2)

so the answer is D

puma wrote:

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Re: sequence [#permalink]

13 Apr 2008, 14:11

I will go with D as welll..

option 3 is a geometric squence..and its sum may not be a sequence..

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Re: sequence [#permalink]

14 Apr 2008, 22:00

Agree with D - Whats the OA ?

Re: sequence [#permalink] 14 Apr 2008, 22:00

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p,r,s,t,u An arithmetic sequance is a sequence in which each

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p,r,s,t,u An arithmetic sequance is a sequence in which each

p,r,s,t,u An arithmetic sequance is a sequence in which each

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