Check GMAT Club Decision Tracker for the Latest School Decision Releases https://gmatclub.com/AppTrack
GMAT Club

 It is currently 27 Mar 2017, 07:58

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

Adding exponents - Easy but its teasing my brain

Author Message
Intern
Joined: 16 Jul 2008
Posts: 13
Followers: 0

Kudos [?]: 27 [0], given: 0

Show Tags

22 Jul 2008, 16:18
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Hi everyone-

What is the rule in solving this problem:

2 + 2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 + 2^8

a)2^9
b)2 ^10
c) 2^16
d) 2^35
e)2^37

I believe there is a quick way to do this but I can't figure it out.
Thanks
Director
Joined: 12 Jul 2008
Posts: 518
Schools: Wharton
Followers: 22

Kudos [?]: 155 [0], given: 0

Show Tags

22 Jul 2008, 16:29
djdela wrote:
Hi everyone-

What is the rule in solving this problem:

2 + 2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 + 2^8

a)2^9
b)2 ^10
c) 2^16
d) 2^35
e)2^37

I believe there is a quick way to do this but I can't figure it out.
Thanks

Are you sure this question is correct?

2 + 2^2 + 2^3 + ... + 2^8 = 510
2^9 = 512
Manager
Joined: 15 Jul 2008
Posts: 207
Followers: 3

Kudos [?]: 59 [0], given: 0

Show Tags

22 Jul 2008, 18:12
The question as is also looks correct. Take 2+2 as 4 or 2^2. This becomes a geometric series with first term 2^2 and ratio=2
Director
Joined: 01 Jan 2008
Posts: 626
Followers: 5

Kudos [?]: 180 [0], given: 1

Show Tags

22 Jul 2008, 18:18
djdela wrote:
What is the rule in solving this problem:

2 + 2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 + 2^8

It probably was 2^2+2^2+2^3 + ...

the rule is very simple 2^k+2^k = 2*2^k = 2^(k+1)

2^2+2^2 = 2^3, then 2^3+2^3 = 2^4, ... , 2^8+2^8 = 2^9
Director
Joined: 12 Jul 2008
Posts: 518
Schools: Wharton
Followers: 22

Kudos [?]: 155 [0], given: 0

Show Tags

22 Jul 2008, 18:33
maratikus wrote:
djdela wrote:
What is the rule in solving this problem:

2 + 2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 + 2^8

It probably was 2^2+2^2+2^3 + ...

the rule is very simple 2^k+2^k = 2*2^k = 2^(k+1)

2^2+2^2 = 2^3, then 2^3+2^3 = 2^4, ... , 2^8+2^8 = 2^9

This makes much more sense.
Intern
Joined: 01 May 2008
Posts: 10
Followers: 0

Kudos [?]: 0 [0], given: 0

Show Tags

22 Jul 2008, 18:50
Hey..

i guess u r all complicating things here..

its is like
2^(1+1+3+4+5+6+7+8) = 2^35
Senior Manager
Joined: 18 Jun 2007
Posts: 294
Followers: 2

Kudos [?]: 56 [0], given: 0

Show Tags

22 Jul 2008, 18:50
take the short form of the series.
=> 2 + 2 + 2^2 + 2^3
=> 2(1 + 1 + 2 + 2^2)
=> 2(2 + 2 + 2^2)
=> 2x2 (1 + 1 + 2)
=> 2x2x2 ( 1+1)
=> 2^3 (2) = 2^4

Through same mechanism given sequence will end in 2^8 (2) = 2^9

Last edited by rishi2377 on 22 Jul 2008, 19:01, edited 1 time in total.
Intern
Joined: 01 May 2008
Posts: 10
Followers: 0

Kudos [?]: 0 [0], given: 0

Show Tags

22 Jul 2008, 18:54
Re: Adding exponents - Easy but its teasing my brain   [#permalink] 22 Jul 2008, 18:54
Display posts from previous: Sort by