It is currently 15 Jan 2018, 23:59

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 digits are in (8×10^14)(10×10^10)?

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

Hide Tags

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43292

Kudos [?]: 139136 [0], given: 12776

How many digits are in (8×10^14)(10×10^10)? [#permalink]

Show Tags

New post 25 Apr 2016, 23:53
Expert's post
5
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

68% (00:29) correct 32% (00:38) wrong based on 169 sessions

HideShow timer Statistics

Kudos [?]: 139136 [0], given: 12776

Manager
Manager
avatar
B
Joined: 01 Jul 2010
Posts: 62

Kudos [?]: 11 [0], given: 6

Location: India
GMAT 1: 660 Q43 V38
GPA: 3.4
GMAT ToolKit User
Re: How many digits are in (8×10^14)(10×10^10)? [#permalink]

Show Tags

New post 26 Apr 2016, 05:41
1
This post was
BOOKMARKED
The question simplfies to (8×10^14)(10^11)
=> 8*10^25
=> Will contain 25 zeros +1 digit 8
=>26

Ans C

Kudos [?]: 11 [0], given: 6

Senior Manager
Senior Manager
User avatar
G
Joined: 13 Apr 2013
Posts: 259

Kudos [?]: 94 [0], given: 682

Location: India
Concentration: International Business, Operations
Schools: ISB '19
GMAT 1: 480 Q38 V22
GPA: 3.01
WE: Engineering (Consulting)
Premium Member CAT Tests
Re: How many digits are in (8×10^14)(10×10^10)? [#permalink]

Show Tags

New post 30 Dec 2017, 22:21
Bunuel wrote:
How many digits are in (8×10^14)(10×10^10)?

A. 24
B. 25
C. 26
D. 27
E. 28


Bunuel can you help me in this. Though I know the concept, still I am counting it as 27.

(8×10^14) ; 10^14 means fourteen "0s" and one "1" So total 15 digits ; 8 does not change the number of digits

(10×10^10) ; 10^11 means 12 digits

So 15+12 = 27
_________________

"Success is not as glamorous as people tell you. It's a lot of hours spent in the darkness."

Kudos [?]: 94 [0], given: 682

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43292

Kudos [?]: 139136 [0], given: 12776

Re: How many digits are in (8×10^14)(10×10^10)? [#permalink]

Show Tags

New post 30 Dec 2017, 22:30
QZ wrote:
Bunuel wrote:
How many digits are in (8×10^14)(10×10^10)?

A. 24
B. 25
C. 26
D. 27
E. 28


Bunuel can you help me in this. Though I know the concept, still I am counting it as 27.

(8×10^14) ; 10^14 means fourteen "0s" and one "1" So total 15 digits ; 8 does not change the number of digits

(10×10^10) ; 10^11 means 12 digits

So 15+12 = 27


You cannot add like that. For example, 10 has 2 digits but 10*10 does not have 2 + 2 = 4 digits it has 3 digits.

You should do the following way: (8×10^14)(10×10^10) = 8*10^25 --> 10^25 has 26 digits. Multiplying it by 8 does not change the number of digits.

Answer: C.
_________________

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

Kudos [?]: 139136 [0], given: 12776

Senior Manager
Senior Manager
User avatar
G
Joined: 13 Apr 2013
Posts: 259

Kudos [?]: 94 [0], given: 682

Location: India
Concentration: International Business, Operations
Schools: ISB '19
GMAT 1: 480 Q38 V22
GPA: 3.01
WE: Engineering (Consulting)
Premium Member CAT Tests
Re: How many digits are in (8×10^14)(10×10^10)? [#permalink]

Show Tags

New post 30 Dec 2017, 22:39
Bunuel wrote:
QZ wrote:
Bunuel wrote:
How many digits are in (8×10^14)(10×10^10)?

A. 24
B. 25
C. 26
D. 27
E. 28


Bunuel can you help me in this. Though I know the concept, still I am counting it as 27.

(8×10^14) ; 10^14 means fourteen "0s" and one "1" So total 15 digits ; 8 does not change the number of digits

(10×10^10) ; 10^11 means 12 digits

So 15+12 = 27


You cannot add like that. For example, 10 has 2 digits but 10*10 does not have 2 + 2 = 4 digits it has 3 digits.

You should do the following way: (8×10^14)(10×10^10) = 8*10^25 --> 10^25 has 26 digits. Multiplying it by 8 does not change the number of digits.

Answer: C.


Can we deduce that number less than 10 does not change the number of digits ever?
_________________

"Success is not as glamorous as people tell you. It's a lot of hours spent in the darkness."

Kudos [?]: 94 [0], given: 682

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43292

Kudos [?]: 139136 [0], given: 12776

Re: How many digits are in (8×10^14)(10×10^10)? [#permalink]

Show Tags

New post 30 Dec 2017, 22:47
QZ wrote:
Bunuel wrote:
QZ wrote:

Bunuel can you help me in this. Though I know the concept, still I am counting it as 27.

(8×10^14) ; 10^14 means fourteen "0s" and one "1" So total 15 digits ; 8 does not change the number of digits

(10×10^10) ; 10^11 means 12 digits

So 15+12 = 27


You cannot add like that. For example, 10 has 2 digits but 10*10 does not have 2 + 2 = 4 digits it has 3 digits.

You should do the following way: (8×10^14)(10×10^10) = 8*10^25 --> 10^25 has 26 digits. Multiplying it by 8 does not change the number of digits.

Answer: C.


Can we deduce that number less than 10 does not change the number of digits ever?


It won't if you have a*10^n, where a is a single digit integer. But for other cases it might not be true. For example, 3*400.
_________________

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

Kudos [?]: 139136 [0], given: 12776

Expert Post
Math Expert
User avatar
D
Joined: 02 Aug 2009
Posts: 5511

Kudos [?]: 6398 [0], given: 122

Re: How many digits are in (8×10^14)(10×10^10)? [#permalink]

Show Tags

New post 30 Dec 2017, 22:56
QZ wrote:
Bunuel wrote:
QZ wrote:
How many digits are in (8×10^14)(10×10^10)?

A. 24
B. 25
C. 26
D. 27
E. 28

Bunuel can you help me in this. Though I know the concept, still I am counting it as 27.

(8×10^14) ; 10^14 means fourteen "0s" and one "1" So total 15 digits ; 8 does not change the number of digits

(10×10^10) ; 10^11 means 12 digits

So 15+12 = 27


You cannot add like that. For example, 10 has 2 digits but 10*10 does not have 2 + 2 = 4 digits it has 3 digits.

You should do the following way: (8×10^14)(10×10^10) = 8*10^25 --> 10^25 has 26 digits. Multiplying it by 8 does not change the number of digits.

Answer: C.


Can we deduce that number less than 10 does not change the number of digits ever?



Hi..
You can't take that as a rule..
It depends on other factors too..
8*10^2.... 8 will not effect
8*20^2.... 8 will effect...

Why you have gone wrong is that you have separated the 10s..
(8*10^14)(10*10^11)....
Although you have correctly solved 10*10^11, you have added an extra digit of 1 from 10^14..
10*10^11 could have meant 10 - 2 digits and 10^10- 10 zeroesand 1 digit for '1', so 10+1=11 digits
Total 2+11=13digits.. but is it so ...NO
It is 12 digits because 10*10^10=10^11, meaning 12 digits
_________________

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/-

Kudos [?]: 6398 [0], given: 122

Re: How many digits are in (8×10^14)(10×10^10)?   [#permalink] 30 Dec 2017, 22:56
Display posts from previous: Sort by

How many digits are in (8×10^14)(10×10^10)?

  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®.