TestMagic

Crack_it!! · 2009 June 30th, 09:00 AM

Q) In the arithmetic sequence t1, t2, t3,........, tn,......t1 = 23 and tn = t(n-1) - 3 for each n>1. What is the value of n when tn = -4
Note: 1,2,3....,n-1,n are all subscripts to 't'.

-1
7
10
14
20

Just not getting the hang of this question. Would appreciate if the answer is given along with the explanation.

Thank you!!

12rk34 · 2009 June 30th, 02:22 PM

t1 = 23
t2 = t1 - 3 = 23-3 = 20
t3 = t2 - 3 = 20 - 3 = 17
It is an arithmetic series with first term t1 = 23,
common difference d= 20-23 = -3
nth term tn = -4
tn = t1 +(n-1)*d
-4 = 23 - (n-1)*3
n - 1 = 27/3 = 9
n = 10
Hence C.

Crack_it!! · 2009 June 30th, 02:53 PM

Quote:

Originally Posted by 12rk34

t1 = 23
t2 = t1 - 3 = 23-3 = 20
t3 = t2 - 3 = 20 - 3 = 17
It is an arithmetic series with first term t1 = 23,
common difference d= 20-23 = -3
nth term tn = -4
tn = t1 +(n-1)*d
-4 = 23 - (n-1)*3
n - 1 = 27/3 = 9
n = 10
Hence C.

I guess, I got to read the question more clearly.
Thank you. Very well explained!!

rajatmeh · 2009 July 1st, 11:54 AM

yes C

eravi11 · 2009 July 1st, 04:55 PM

C it is

saravanants · 2009 July 2nd, 08:29 PM

Yes C (TT:76 seconds)

abhishek_mumbai · 2009 July 3rd, 01:33 PM

Yes.. C

MBA2010HereWeGo · 2009 July 3rd, 06:38 PM

Concur with C

kranti_surya · 2009 July 3rd, 08:24 PM

1 2 3 4 5 6 7 8 9 10
23, 20, 17, 14, 11, 8, 5, 2, -1, -4

Imo C

2009 June 30th, 09:00 AM	#1 (permalink)
Crack_it!! Within my grasp! Join Date: Mar 2009 Posts: 129	Series Q) In the arithmetic sequence t1, t2, t3,........, tn,......t1 = 23 and tn = t(n-1) - 3 for each n>1. What is the value of n when tn = -4 Note: 1,2,3....,n-1,n are all subscripts to 't'. -1 7 10 14 20 Just not getting the hang of this question. Would appreciate if the answer is given along with the explanation. Thank you!!

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

2009 June 30th, 02:22 PM	#2 (permalink)
12rk34 TestMagic Guru Join Date: Jun 2008 Posts: 1,566	t1 = 23 t2 = t1 - 3 = 23-3 = 20 t3 = t2 - 3 = 20 - 3 = 17 It is an arithmetic series with first term t1 = 23, common difference d= 20-23 = -3 nth term tn = -4 tn = t1 +(n-1)d -4 = 23 - (n-1)3 n - 1 = 27/3 = 9 n = 10 Hence C.

2009 July 1st, 11:54 AM	#4 (permalink)
rajatmeh TestMagic Guru Join Date: Jan 2009 Posts: 1,014	yes C

2009 July 1st, 04:55 PM	#5 (permalink)
eravi11 So far So bad! Join Date: Feb 2009 Posts: 630	C it is

2009 July 2nd, 08:29 PM	#6 (permalink)
saravanants Eager! Join Date: Jun 2009 Posts: 54	Yes C (TT:76 seconds)

2009 July 3rd, 01:33 PM	#7 (permalink)
abhishek_mumbai Done with GMAT - 700 Join Date: Apr 2009 Location: Pune, India Posts: 1,182	Yes.. C

2009 July 3rd, 06:38 PM	#8 (permalink)
MBA2010HereWeGo Within my grasp! Join Date: Jun 2009 Location: Seattle, WA Posts: 257	Concur with C

2009 July 3rd, 08:24 PM	#9 (permalink)
kranti_surya I can crack it Join Date: Apr 2009 Location: San Francisco Posts: 201	1 2 3 4 5 6 7 8 9 10 23, 20, 17, 14, 11, 8, 5, 2, -1, -4 Imo C

TestMagic

Free GMAT, GRE, SAT Test, TOEFL practice tests