NEW HERE? LEARN MORE
closeclose
Last visit was: 23 Apr 2024, 17:47 It is currently 23 Apr 2024, 17:47
Decision Tracker
My Rewards
New posts
New comers' posts

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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

A sum of money doubles itself at a compound interest in 15 years. In

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92883
Own Kudos [?]: 618597 [24]
Given Kudos: 81563
Send PM
CAT Tests Forum Quiz Mode
A sum of money doubles itself at a compound interest in 15 years. In [#permalink] New post   Updated on: 26 Feb 2019, 04:35
24
Bookmarks
Expert Reply
00:00
A
B
C
D
E

Difficulty:

15% (low)

Question Stats:

73% (00:57) correct 27% (01:15) wrong based on 774 sessions
Hide Show timer Statistics
A sum of money doubles itself at a compound interest in 15 years. In how may years it will become 8 times ??


A. 30 years

B. 40 years

C. 45 years

D. 50 years

E. 60 years
ShowHide Answer
Official Answer
C

Originally posted by Bunuel on 07 Feb 2014, 03:56.
Last edited by Bunuel on 26 Feb 2019, 04:35, edited 1 time in total.
Renamed the topic and edited the question.
Most Helpful Reply
avatar
PareshGmat
SVP
SVP
Joined: 27 Dec 2012
Status:The Best Or Nothing
Posts: 1562
Own Kudos [?]: 7207 [12]
Given Kudos: 193
Location: India
Concentration: General Management, Technology
WE:Information Technology (Computer Software)
Send PM
Re: A sum of money doubles itself at a compound interest in 15 years. In [#permalink] New post   13 Aug 2014, 02:15
10
Kudos
2
Bookmarks
Say initial amount = 100

Final amount = 800

100 >>>>>>>> 200 >>>>>>>>> 400 >>>>>>>>>> 800

........... 15 ............ 15 ................. 15

Total = 15*3 = 45

Answer = C
General Discussion
avatar
unceldolan
Manager
Manager
Joined: 21 Oct 2013
Posts: 154
Own Kudos [?]: 212 [4]
Given Kudos: 19
Location: Germany
Schools: Owen '17 (A$) Sauder '17 (A$) Schulich '17 (WD) Anderson FEMBA '17 (S) McDonough '17 (A) Desautels '17 (S)
GMAT 1: 660 Q45 V36
GPA: 3.51
Send PM
Re: A sum of money doubles itself at a compound interest in 15 years. In [#permalink] New post   11 Aug 2014, 01:44
3
Kudos
1
Bookmarks
Let's say amount of money = $2, then 8 times = 16 $

Then
Year 00 = 2 $
Year 15 = 4 $
Year 30 = 8 $
Year 45 = 16 $ --> this is our answer, hence C.
User avatar
S
Nunuboy1994
Director
Director
Joined: 12 Nov 2016
Posts: 569
Own Kudos [?]: 118 [0]
Given Kudos: 167
Location: United States
Schools: Yale '18
GMAT 1: 650 Q43 V37
GRE 1: Q157 V158
GPA: 2.66
Send PM
Re: A sum of money doubles itself at a compound interest in 15 years. In [#permalink] New post   21 Jun 2017, 05:18
Bunuel wrote:
aimlockfire1 wrote:
A sum of money doubles itself at a compound interest in 15 years . In how may years it will become 8 times ??

a) 30 years

b) 40 years

c) 45 years

d) 50 years

e) 60 years


If the sum doubles (x2) in 15 years, then it to become 2*2*2 = 8 times as large it should double three times, so three 15 years time period are needed, which is 3*15 = 45 years.

Answer: C.


If the lump sum is 8x then this represents a 2x^3 increase to

x(1 +r)^15(3)= 8x

Thus
"C"
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92883
Own Kudos [?]: 618597 [1]
Given Kudos: 81563
Send PM
CAT Tests Forum Quiz Mode
Re: A sum of money doubles itself at a compound interest in 15 years. In [#permalink] New post   26 Feb 2019, 04:36
1
Kudos
Expert Reply
Bunuel wrote:
A sum of money doubles itself at a compound interest in 15 years. In how may years it will become 8 times ??


A. 30 years

B. 40 years

C. 45 years

D. 50 years

E. 60 years


If the sum doubles (*2) in 15 years, then it to become 2*2*2 = 8 times as large it should double three times, so three 15 years time period are needed, which is 3*15 = 45 years.

Answer: C.
avatar
B
njnikhiljindal567
Intern
Intern
Joined: 08 Apr 2019
Posts: 6
Own Kudos [?]: 12 [3]
Given Kudos: 104
Send PM
Re: A sum of money doubles itself at a compound interest in 15 years. In [#permalink] New post   25 Apr 2019, 03:58
2
Kudos
We can use the standard Compound interest formula for this -

let x be the amount of money invested

2x = x(1+ r/100)^15........................eq 1

Now to want to find the how much time it will take for 8x

Which is (eq1)^3

Hence 8x = x(1 +r/100)^45

Hence C
User avatar
D
exc4libur
SVP
SVP
Joined: 24 Nov 2016
Posts: 1720
Own Kudos [?]: 1344 [1]
Given Kudos: 607
Location: United States
Send PM
Re: A sum of money doubles itself at a compound interest in 15 years. In [#permalink] New post   22 Aug 2019, 09:54
1
Kudos
Bunuel wrote:
A sum of money doubles itself at a compound interest in 15 years. In how may years it will become 8 times ??

A. 30 years
B. 40 years
C. 45 years
D. 50 years
E. 60 years


\(a(1+r)^{(15)}=2a…(1+r)^{(15)}=2…(1+r)=2^{(1/15)}\)
\((1+r)^x=8…(2^{(1/15)})^{x}=8…2^x=8^{(15)}…2^x=(2^3)^{(15)}…x=3•15=45\)

Answer (C)
User avatar
B
Farina
Manager
Manager
Joined: 21 Aug 2019
Posts: 105
Own Kudos [?]: 42 [0]
Given Kudos: 353
Send PM
Re: A sum of money doubles itself at a compound interest in 15 years. In [#permalink] New post   14 Feb 2020, 05:01
Amount will be doubled in every 15 years
Let the initial amount is 100
so in 15 years it will be 100 * 2 = 200
in next 15 years it will be 200 * 2 = 400
and again in 15 years it will be 400 * 2 = 800

so 15+15+15 = 45 years Option C
User avatar
L
ScottTargetTestPrep
Target Test Prep Representative
Joined: 14 Oct 2015
Status:Founder & CEO
Affiliations: Target Test Prep
Posts: 18753
Own Kudos [?]: 22041 [2]
Given Kudos: 283
Location: United States (CA)
Send PM
Re: A sum of money doubles itself at a compound interest in 15 years. In [#permalink] New post   01 Jan 2021, 05:53
2
Kudos
Expert Reply
Bunuel wrote:
A sum of money doubles itself at a compound interest in 15 years. In how may years it will become 8 times ??


A. 30 years

B. 40 years

C. 45 years

D. 50 years

E. 60 years

Solution:

If it takes 15 years to double the amount of an investment, then it takes another 15 years (or a total of 30 years) to double it again, making it 4 times the original amount. Finally, it takes another 15 years (or a total of 45 years) to double it again, making it 8 times the original amount.

Answer: C
User avatar
bumpbot
Non-Human User
Joined: 09 Sep 2013
Posts: 32629
Own Kudos [?]: 821 [0]
Given Kudos: 0
Send PM
Re: A sum of money doubles itself at a compound interest in 15 years. In [#permalink] New post   16 Aug 2023, 04:47
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.
GMAT Club Bot
gmatclubot
Re: A sum of money doubles itself at a compound interest in 15 years. In [#permalink]
16 Aug 2023, 04:47
Moderators:
Bunuel
Math Expert
92883 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions