It is currently 21 Jan 2018, 22:37

Close

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
Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

How many different sums can be formed by adding 2 different numbers f

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Expert Post
Math Revolution GMAT Instructor
User avatar
D
Joined: 16 Aug 2015
Posts: 4705
GPA: 3.82
Premium Member
How many different sums can be formed by adding 2 different numbers f [#permalink]

Show Tags

New post 27 Dec 2017, 23:42
Expert's post
1
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

87% (01:38) correct 13% (01:31) wrong based on 31 sessions

HideShow timer Statistics

[GMAT math practice question]

How many different sums can be formed by adding \(2\) different numbers from the set {\(1, 2, 4, 8, 16, 32, 33\)}?

A. \(16\)
B. \(17\)
C. \(18\)
D. \(19\)
E. \(20\)
[Reveal] Spoiler: OA

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
Find a 10% off coupon code for GMAT Club members.
“Receive 5 Math Questions & Solutions Daily”
Unlimited Access to over 120 free video lessons - try it yourself
See our Youtube demo

Expert Post
Math Expert
User avatar
D
Joined: 02 Aug 2009
Posts: 5537
Re: How many different sums can be formed by adding 2 different numbers f [#permalink]

Show Tags

New post 28 Dec 2017, 04:58
MathRevolution wrote:
[GMAT math practice question]

How many different sums can be formed by adding \(2\) different numbers from the set {\(1, 2, 4, 8, 16, 32, 33\)}?

A. \(16\)
B. \(17\)
C. \(18\)
D. \(19\)
E. \(20\)



choose 2 out of 7 \(= 7C2=\frac{7!}{5!2!}=21\)
however 1+33 is SAME as 2+32, so subtract 1 to get different SUM = 21-1=20
E

NOTE :- one of the choices should have been 21 to make it more challenging
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html


BANGALORE/-

Expert Post
Math Revolution GMAT Instructor
User avatar
D
Joined: 16 Aug 2015
Posts: 4705
GPA: 3.82
Premium Member
Re: How many different sums can be formed by adding 2 different numbers f [#permalink]

Show Tags

New post 01 Jan 2018, 01:23
=>
All choices of two different numbers from this set give rise to different sums apart from \(1 + 33\) and \(2 + 32\).
The number of ways to choose \(2\) numbers from the set {\(1, 2, 4, 8, 16, 32, 33\)} of \(7\) numbers is 7C2 = \(\frac{(7*6)}{(1*2)}\) = \(21\).
Since two of these choices, \(1, 33\) and \(2, 32\), have the same sum, we need to subtract \(1\) from \(21\).
Then we have \(21 – 1 = 20\) possible choices.

Therefore, the answer is E.
Answer: E
_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
Find a 10% off coupon code for GMAT Club members.
“Receive 5 Math Questions & Solutions Daily”
Unlimited Access to over 120 free video lessons - try it yourself
See our Youtube demo

Re: How many different sums can be formed by adding 2 different numbers f   [#permalink] 01 Jan 2018, 01:23
Display posts from previous: Sort by

How many different sums can be formed by adding 2 different numbers f

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

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®.