It is currently 27 Jun 2017, 21:23

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# What is the tenth term in a series of 89 consecutive

Author Message
TAGS:

### Hide Tags

Manager
Joined: 28 Feb 2003
Posts: 100
What is the tenth term in a series of 89 consecutive [#permalink]

### Show Tags

17 May 2003, 03:00
6
This post was
BOOKMARKED
00:00

Difficulty:

25% (medium)

Question Stats:

67% (01:55) correct 33% (01:03) wrong based on 389 sessions

### HideShow timer Statistics

What is the tenth term in a series of 89 consecutive positive integers?

(1) The average of the integers is 100
(2) The 79th term in the series is 134
[Reveal] Spoiler: OA
Intern
Joined: 26 Mar 2003
Posts: 24

### Show Tags

17 May 2003, 11:26
D.

From (1) You know term 45 is 100.
From (2) You know term 79 is 134.

From either, you can calculate the 10th term = 65.
Intern
Joined: 17 May 2003
Posts: 2

### Show Tags

21 May 2003, 01:11
Thanks brstorewala for sharing this interesting math DS problem.
I wonder where are the source to get all these questions?

I already studied the Kaplan book, but wasn't feeling it too helpful.
I got most questions right in practice but I didn't do that well in real GMAT test with the time concern. Any suggestion?
Manager
Joined: 28 Feb 2003
Posts: 100

### Show Tags

21 May 2003, 01:29
With almost two minutes for each question on the math section and around 110 sec for each question on the verbal section, time does not seem to be a major concern. The problem is that the mind goes blank. I experienced it when I took my PP test at home. Especially for the RC part, I was not able to think clearly. It was like my mind was clouded and I was blank. So it is really a matter of how calm and composed you are, assuming that you have practiced sufficiently. I am a proponent of the philosophy of "practice as much as u can"......2k, 5k, 10k......any number of questions....the key is getting a feel, making sure that you don't see a different "kind" of a problem in the exam. Of course strategy is important, so I make this summary kind of a thing for each section, in which i note down the main testing points and rules. The summary would be very handy toward the end of your preparation schedule. Those are my two cents.....i am just waiting to see how my philosophy and strategy work on the "D" day.........it all boils down to those 4 bloody hours.......
SVP
Joined: 03 Feb 2003
Posts: 1604

### Show Tags

21 May 2003, 02:49
brstorewala wrote:
With almost two minutes for each question on the math section and around 110 sec for each question on the verbal section, time does not seem to be a major concern. The problem is that the mind goes blank. I experienced it when I took my PP test at home. Especially for the RC part, I was not able to think clearly. It was like my mind was clouded and I was blank. So it is really a matter of how calm and composed you are, assuming that you have practiced sufficiently. I am a proponent of the philosophy of "practice as much as u can"......2k, 5k, 10k......any number of questions....the key is getting a feel, making sure that you don't see a different "kind" of a problem in the exam. Of course strategy is important, so I make this summary kind of a thing for each section, in which i note down the main testing points and rules. The summary would be very handy toward the end of your preparation schedule. Those are my two cents.....i am just waiting to see how my philosophy and strategy work on the "D" day.........it all boils down to those 4 bloody hours.......

Cool... A sort of philosophy... Brstorewala, have you ever tried to write a philosophic treatise? You are to be successful. No doubt.
Intern
Joined: 17 May 2003
Posts: 2

### Show Tags

22 May 2003, 23:01
great advice. comprehension is also my weakest part.
usually how much time people spend on preparing for the gmat?
3 months? 6 months?
Math Expert
Joined: 02 Sep 2009
Posts: 39725

### Show Tags

26 Nov 2009, 11:35
1
KUDOS
Expert's post
2
This post was
BOOKMARKED
brstorewala wrote:
What is the tenth term in a series of 89 consecutive positive integers?
1) The average of the integers is 100
2) The 79th term in the series is 134

Consecutive integers represent arithmetic progression.

For AP:
Sequence $$A1, A2, ... An$$ so that $$A(n)=A(n-1)+d$$ (d constant, common difference).

$$An=A1 + d*(n-1)$$ - formula for nth term.

$$Sn=n*\frac{(A1+An)}{2}$$ or $$Sn=n*\frac{2*A1+d(n-1)}{2}$$ - formula for sum of AP.

In case AP is consecutive integers we'll get common difference, $$d$$, as $$1$$. So:

$$An=A1+n-1$$ - formula for nth term

$$Sn=n*\frac{(A1+An)}{2}$$ or $$Sn=n*\frac{2*A1+n-1}{2}$$ - formula for sum of AP.

(1) The average of the integers is 100

--> $$Sum=89*100=8900$$

--> $$Sn=n*\frac{2*A1+n-1}{2}=8900$$, $$n=89$$

--> $$89*\frac{2*A1+89-1}{2}=8900$$.

--> $$A1=56$$

--> $$An=A1+n-1$$

--> $$A10=A1+10-1=56+10-1=65$$.

Sufficient.

(2) The 79th term in the series is 134

--> $$A79=134=A1+79-1$$

--> $$A1=56$$

--> $$An=A1+n-1$$

--> $$A10=A1+10-1=56+10-1=65$$.

Sufficient.

_________________
Joined: 20 Aug 2009
Posts: 306
Location: Tbilisi, Georgia
Schools: Stanford (in), Tuck (WL), Wharton (ding), Cornell (in)

### Show Tags

26 Nov 2009, 13:45
There is a very good explanation of consecutive integers in MGMAT Number Properties.

If you can calculate first term of the series than you can calculate everything else ($$A_1$$ and $$n$$ define every other term, also average and sum)
Manager
Joined: 22 Sep 2009
Posts: 215
Location: Tokyo, Japan

### Show Tags

27 Nov 2009, 10:21
Damn, thanks a bunch, Bunuel
I completely miss the CONSECUTIVE part... hence did not realize d=1
Manager
Joined: 22 Sep 2009
Posts: 215
Location: Tokyo, Japan

### Show Tags

28 Nov 2009, 00:41
On a second thought, does consecutive always imply the numbers need to be increasing? Otherwise d=-1 is also possible from the given statements?
SVP
Joined: 29 Aug 2007
Posts: 2473

### Show Tags

28 Nov 2009, 22:24
lonewolf wrote:
On a second thought, does consecutive always imply the numbers need to be increasing? Otherwise d=-1 is also possible from the given statements?

I think consecutive +ve integers are : 2, 3, 4, 5, and n but not n, ...............10, 9, 8, 7, 6 ..............1.

In that sense, answer should be D. However your thinking is also valuable if it were a +ve series only.

brstorewala wrote:
What is the tenth term in a series of 89 consecutive positive integers?
1) The average of the integers is 100
2) The 79th term in the series is 134

_________________

Gmat: http://gmatclub.com/forum/everything-you-need-to-prepare-for-the-gmat-revised-77983.html

GT

Founder
Joined: 04 Dec 2002
Posts: 15151
Location: United States (WA)
GMAT 1: 750 Q49 V42

### Show Tags

28 Nov 2009, 22:47
Wow - you guys found some really old question from 2003!!!
_________________

Founder of GMAT Club

US News Rankings progression - last 10 years in a snapshot - New!
Just starting out with GMAT? Start here...
Need GMAT Book Recommendations? Best GMAT Books

Co-author of the GMAT Club tests

Manager
Joined: 24 Dec 2009
Posts: 219

### Show Tags

18 Aug 2010, 10:59
It is D.

And answer is 65 --- 10th term in series.

A ) Using the average, find the midpoint of series. It will be 45th term with values of 89*100/89 = 100. To get 10th term, there are 35 jumps of 1 point worth each. Hence 10th term = 100 - 35 * 1= 65.

A is sufficient.

B) Similarly here 79th term is 134. To reach 10th term, there are 69 jumps worth 1 point each. Hence 10th term = 134 - 69 = 65.

B is sufficient.

Hence correct answer choice is D.

Thanks,
Akhil M.Parekh
Manager
Joined: 07 Aug 2010
Posts: 79

### Show Tags

10 Oct 2010, 15:59
1
KUDOS
D

1) since these are consecutive intergers, mean will be the middle number... walk back to find the 10th

2) 79th term is know, so walk back to find the 10th term.... again, since these are consecutive integers
_________________

Click that thing - Give kudos if u like this

GMAT Club Legend
Joined: 09 Sep 2013
Posts: 16014
Re: What is the tenth term in a series of 89 consecutive [#permalink]

### Show Tags

25 Sep 2015, 13:35
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Senior Manager
Joined: 17 Jun 2015
Posts: 263
GMAT 1: 540 Q39 V26
GMAT 2: 680 Q46 V37
Re: What is the tenth term in a series of 89 consecutive [#permalink]

### Show Tags

24 Dec 2015, 07:32
Consecutive integers means they are all distinct and are in AP.

In an AP with odd number of term the median and the mean are the same.

Statement 1:
100 is the mean and also the median. So 100 is the 45th terms. We just subtract 44 and get the answer. Also, it works becasue they are consecutive integer. Had it been an AP of non consecutive integers, this wouldn't have worked

Anyways, the statement is sufficient

Statement 2:
Gives one of the terms
The common difference is 1 (consecutive integers)

Sufficient to back track or use AP formulas to find any other term in the series.

Hence Each statement alone is sufficient. D
_________________

Fais de ta vie un rêve et d'un rêve une réalité

Director
Joined: 04 Jun 2016
Posts: 650
GMAT 1: 750 Q49 V43
What is the tenth term in a series of 89 consecutive [#permalink]

### Show Tags

16 Jul 2016, 02:20
brstorewala wrote:
What is the tenth term in a series of 89 consecutive positive integers?

(1) The average of the integers is 100
(2) The 79th term in the series is 134

(1) The average of the integers is 100
Sufficient
(first+last term)/2=100
first + last =200
since there are total of 89 numbers and all numbers are consecutive; therefore last term = first+88
First+(First+88)=200
2*first=112
FIRST TERM=56
the first term is 56 therefore the tenth term will be 65
SUFFICIENT

(2) The 79th term in the series is 134
SUFFICIENT:-
79 term is 134, so we can reverse count the 10th term
or (79th-69th) term = (134-69)
or 10th term =65

_________________

Posting an answer without an explanation is "GOD COMPLEX". The world doesn't need any more gods. Please explain you answers properly.
FINAL GOODBYE :- 17th SEPTEMBER 2016. .. 16 March 2017 - I am back but for all purposes please consider me semi-retired.

What is the tenth term in a series of 89 consecutive   [#permalink] 16 Jul 2016, 02:20
Similar topics Replies Last post
Similar
Topics:
3 What is the average (arithmetic mean) of a series of N consecutive odd 4 20 Nov 2016, 11:17
1 What is the sum of the terms in a sequence of consecutive multiples of 1 05 Sep 2016, 09:12
1 What is the sum of the terms in a sequence of consecutive integers? 5 16 Jul 2016, 03:22
4 What is the sum of the terms in a certain sequence of consecutive in a 3 09 May 2017, 08:42
3 What is the tenths digit in the decimal representation of a 7 03 May 2014, 04:54
Display posts from previous: Sort by