GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 17 Aug 2018, 00:24

### 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

# If the a-th term of a certain sequence is given by (-1)^a + (-0.1)^a

Author Message
TAGS:

### Hide Tags

Director
Joined: 07 Aug 2011
Posts: 560
GMAT 1: 630 Q49 V27
If the a-th term of a certain sequence is given by (-1)^a + (-0.1)^a  [#permalink]

### Show Tags

Updated on: 09 Apr 2015, 06:26
3
00:00

Difficulty:

35% (medium)

Question Stats:

73% (02:01) correct 27% (01:51) wrong based on 85 sessions

### HideShow timer Statistics

If the a-th term of a certain sequence is given by $$(-1)^a + (-0.1)^a,$$ then the sum of the terms from 1 to 5 is

A. -1.11111
B. -1.09091
C. 0
D. 0.90909
E. 1.11111

_________________

Thanks,
Lucky

_______________________________________________________
Kindly press the to appreciate my post !!

Originally posted by Lucky2783 on 09 Apr 2015, 06:00.
Last edited by Bunuel on 09 Apr 2015, 06:26, edited 1 time in total.
Edited the question.
Director
Joined: 07 Aug 2011
Posts: 560
GMAT 1: 630 Q49 V27
Re: If the a-th term of a certain sequence is given by (-1)^a + (-0.1)^a  [#permalink]

### Show Tags

09 Apr 2015, 06:24
Lucky2783 wrote:
If the a-th term of a certain sequence is given by $$(-1)^a + (-0.1)^a,$$ then the sum of the terms from 1 to 5 is
A. -1.11111
B. -1.09091
C. 0
D. 0.90909
E. 1.11111

One of the possible solutions :

the resultant series is

$$(-1)^1+(-1)^2+(-1)^3+(-1)^4+(-1)^5 =\frac{(-1) (1-(-1)^5)}{(1-(-1))}$$ = -1

$$(-0.1)^1+(-0.1)^2+(-0.1)^3+(-0.1)^4+(-0.1)^5 =\frac{(-0.1) (1-(-0.1)^5)}{(1-(-0.1))}$$ = -0.09091

_________________

Thanks,
Lucky

_______________________________________________________
Kindly press the to appreciate my post !!

Intern
Joined: 26 Aug 2014
Posts: 47
GMAT 1: 650 Q49 V30
GMAT 2: 650 Q49 V31
WE: Programming (Computer Software)
Re: If the a-th term of a certain sequence is given by (-1)^a + (-0.1)^a  [#permalink]

### Show Tags

09 Apr 2015, 11:39
When a is 1,3 or 5, we will get a negative number and when it is 2 or 4 we will get a positive number.
Considering the above, we will be left with -1 + (-0.1)^a
So answer choices C, D, and E are eliminated.

Also notice, we will get answer choice A when all results of (-0.1)^a are negative, which is not the case.

So the correct answer is B.

Alternately, you can add the following:

-1 -0.1+0.01-0.001+0.0001-0.00001 = -1.09091

Non-Human User
Joined: 09 Sep 2013
Posts: 7733
Re: If the a-th term of a certain sequence is given by (-1)^a + (-0.1)^a  [#permalink]

### Show Tags

29 Jul 2018, 22:56
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.
_________________
Re: If the a-th term of a certain sequence is given by (-1)^a + (-0.1)^a &nbs [#permalink] 29 Jul 2018, 22:56
Display posts from previous: Sort by

# Events & Promotions

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.