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

It is currently 20 Sep 2018, 11:37

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

Mary is building a pyramid out of stacked rows of soup cans. When comp

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

Hide Tags

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 49271
Mary is building a pyramid out of stacked rows of soup cans. When comp  [#permalink]

Show Tags

New post 05 Jul 2018, 04:57
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

60% (02:17) correct 40% (02:14) wrong based on 25 sessions

HideShow timer Statistics

Mary is building a pyramid out of stacked rows of soup cans. When completed, the top row of the pyramid contains a single soup can, and each row below the top row contains 6 more cans than the one above it. If the completed pyramid contains 16 rows, then how many soup cans did Mary use to build it?

A. 91
B. 96
C. 728
D. 732
E. 736

_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

BSchool Forum Moderator
User avatar
V
Joined: 26 Feb 2016
Posts: 3131
Location: India
GPA: 3.12
Premium Member CAT Tests
Mary is building a pyramid out of stacked rows of soup cans. When comp  [#permalink]

Show Tags

New post 05 Jul 2018, 05:25
Bunuel wrote:
Mary is building a pyramid out of stacked rows of soup cans. When completed, the top row of the pyramid contains a single soup can, and each row below the top row contains 6 more cans than the one above it. If the completed pyramid contains 16 rows, then how many soup cans did Mary use to build it?

A. 91
B. 96
C. 728
D. 732
E. 736


We are told that the top row of the pyramid that Mary is building will contain 1 soup can.
The second row contains 7(1+6) cans. Similarly, the third row contains 12(1+2*6) cans.

This is an arithmetic progression and sum of the terms is \(\frac{n}{2}(2a + (n-1)d)\)

Substituting values - n = 16, a = 1 and d = 7, the sum of terms is \(8(2 + 15*7) = 8*107 = 736\)
Therefore, Mary needs 736(Option C) cans to build the pyramid of soup cans.

Shortcut solution:
Units digits of the 16 digits is {1 + 7 + 3 + 9 + 5}3 times + 1 = 3*15 + 1 = 75 + 1 = 76
Since, the units digit is 6 and number of soup can's > 96. The answer option is 736(Option E)

_________________

You've got what it takes, but it will take everything you've got

Manager
Manager
User avatar
S
Joined: 31 Aug 2016
Posts: 103
Location: India
Concentration: Finance, General Management
GMAT 1: 680 Q49 V33
GPA: 2.81
Premium Member Reviews Badge CAT Tests
Re: Mary is building a pyramid out of stacked rows of soup cans. When comp  [#permalink]

Show Tags

New post 05 Jul 2018, 08:27
Bunuel wrote:
Mary is building a pyramid out of stacked rows of soup cans. When completed, the top row of the pyramid contains a single soup can, and each row below the top row contains 6 more cans than the one above it. If the completed pyramid contains 16 rows, then how many soup cans did Mary use to build it?

A. 91
B. 96
C. 728
D. 732
E. 736


Row1 = 1
row 2 = 1 + 6
row 3 = 1 + 6*2
row 4 = 1 + 6*3
.
.
.
row 16 = 1 + 6 * 15

total cans = 16 + arithmetic sum of 6,12,18,....,90

= 16 + \(\frac{15}{2}\)(12 + 14 *6)

= 736

answer E
_________________

Resources
GMATNinja Webinars
GMATNinja Chats

Quant
Mixtures

Re: Mary is building a pyramid out of stacked rows of soup cans. When comp &nbs [#permalink] 05 Jul 2018, 08:27
Display posts from previous: Sort by

Mary is building a pyramid out of stacked rows of soup cans. When comp

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

Events & Promotions

PREV
NEXT


GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| 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®.