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 Post subject: number sequence
PostPosted: Thu Mar 04, 2010 11:12 am 
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Joined: Sat Jun 21, 2008 11:56 am
Posts: 22
Hi

Pls help for this question

What are the next two numbers of this squence?

1, 1, 2, 4, 6, 12, 15, ____, _____


(a) 33, 31
(b) 16, 31
(c) 33, 16
(d) 16, 33



Thanks


Rds

Uma


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 Post subject:
PostPosted: Thu Mar 04, 2010 6:32 pm 
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Joined: Mon Jun 18, 2007 2:32 pm
Posts: 6962
Location: East Kent
this has been driving me mad all day!

haven;t given up YET though.......


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 Post subject:
PostPosted: Thu Mar 04, 2010 7:51 pm 
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Joined: Mon Jan 05, 2009 9:23 pm
Posts: 514
me too Yoyo!

My colleague and I were trying to work it out earlier for over an hour!!!
I thought at one point that I had got the answer but then when I tried to explain it to my colleague I couldn't get it to come right. The way I worked it out was very complicated!!

I will wait for someone with superior knowledge to me to give the correct answer.


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 Post subject:
PostPosted: Thu Mar 04, 2010 8:09 pm 
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Joined: Sat Jan 12, 2008 6:14 pm
Posts: 162
This has been baffling me too!

I split the sequence into 2 alternating ones
ie 1,2,6,15

and 1,4,12

I think that the first sequence is increasing by the square numbers

ie +1, then +4 then +9 so I would expect it then to increase by +16 making the next term in that sequence to be 31 but I can't see a pattern for the second sequence.

Really hoping someone will shed light soon!

CN


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 Post subject:
PostPosted: Thu Mar 04, 2010 9:06 pm 
Complete Novice wrote:
This has been baffling me too!

I split the sequence into 2 alternating ones
ie 1,2,6,15

and 1,4,12

I think that the first sequence is increasing by the square numbers

ie +1, then +4 then +9 so I would expect it then to increase by +16 making the next term in that sequence to be 31 but I can't see a pattern for the second sequence.

Really hoping someone will shed light soon!

CN


1, 1, 2, 4, 6, 12, 15, ____, _____

The second sequence takes the sum of the 3 numbers before including both sequences ie 4 = 2+1+1, 12= 6+4+2, so the final number must equal 15+12+6 & so is 33

- so the answer is A


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 Post subject: Re: number sequence
PostPosted: Thu Mar 04, 2010 9:48 pm 
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Joined: Mon Feb 20, 2006 1:29 pm
Posts: 1805
Location: Berkshire
Uma wrote:
Hi

Pls help for this question
What are the next two numbers of this squence?
1, 1, 2, 4, 6, 12, 15, ____, _____

(a) 33, 31
(b) 16, 31
(c) 33, 16
(d) 16, 33

Thanks
Rds
Uma


Between DS1 and me, we deduced that;

Sequence 1 goes up in Square numbers...
1, 2, 6, 15, 31 difference between each = 1, 4, 9, 16 (All Square numbers)


1, 1, 2, 4, 6, 12, 15, ____, _____

The sum of two consecutive numbers in the first sequence adds up to the difference of the two consecutive numbers in the second sequence.
1+2 = 3 difference between 1 and 4=3
2+6 = 8 difference between 4 and 12=8
6+15 =21 difference between 12 and 33=21


therefore answer is (a) 33, 31

:D

BW


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 Post subject:
PostPosted: Fri Mar 05, 2010 9:41 am 
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Joined: Mon Jun 18, 2007 2:32 pm
Posts: 6962
Location: East Kent
at last, I was playing around with something similar but couldn;t pin it down..

Can I throw way all these bits of paper now...?


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