It is currently 22 Jun 2017, 19:30

### 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

# If a certain culture of bacteria increases by a constant

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

### Hide Tags

BSchool Forum Moderator
Joined: 27 Aug 2012
Posts: 1193
If a certain culture of bacteria increases by a constant [#permalink]

### Show Tags

29 Aug 2013, 13:31
3
KUDOS
10
This post was
BOOKMARKED
00:00

Difficulty:

85% (hard)

Question Stats:

48% (01:59) correct 52% (01:03) wrong based on 252 sessions

### HideShow timer Statistics

If a certain culture of bacteria increases by a constant factor of x every y minutes, how long will it take for the culture to increase to ten-thousand times its original size?

1. $$x=10^y$$
2.In two minutes, the culture will increase to one hundred times its original size.
[Reveal] Spoiler: OA

_________________
Intern
Joined: 31 Jan 2013
Posts: 17
Schools: ISB '15
WE: Consulting (Energy and Utilities)
Re: If a certain culture of bacteria increases by a constant [#permalink]

### Show Tags

29 Aug 2013, 23:44
1
This post was
BOOKMARKED
My take:

We need to find y, when xy=10^4.

1) When x=10^y, y*(10^y)=10^4
or could also be written as y = 10^(4-y)
By using substitution, we could say y could be between 3 and 4 (~=3.4). Hence st1 is Sufficient
( And Options B,C,&E could be eliminated)

2) (2)*x=100 i.e. x=50. By substituting value of x in xy=10^4, we could find the time taken. Hence st2 is Sufficient

Hence the solution is
[Reveal] Spoiler:
D

/SM
BSchool Forum Moderator
Joined: 27 Aug 2012
Posts: 1193
Re: If a certain culture of bacteria increases by a constant [#permalink]

### Show Tags

01 Sep 2013, 22:05
Hi Bunuel,
It'd be really helpful if you could provide an explanation for this problem to help me understand it.

_________________
Manager
Status: Persevering
Joined: 15 May 2013
Posts: 218
Location: India
GMAT Date: 08-02-2013
GPA: 3.7
WE: Consulting (Consulting)
Re: If a certain culture of bacteria increases by a constant [#permalink]

### Show Tags

08 Sep 2013, 05:40
3
KUDOS
bagdbmba wrote:
Hi Bunuel,
It'd be really helpful if you could provide an explanation for this problem to help me understand it.

Maybe this will help

from 1 we are given x=10^y, let initial quantity be m

So after y minutes the quantity => m*x =>m*10^y , now we need the new value to be 10,000 times the original => m*10^y=m*1000 => y=4 minutes
hence statement 1 is sufficient.

from statement 2

In 2 minutes the culture will increase to 100 times this can be interpreted as follows
1) every 1 minute the quantity is multiplied by 10
or
2) every 2 minutes the quantity is multiplied by 100

Either ways after 4 minutes the quantity will be multiplied by 10,000 hence y=4 minutes

Hence statement 2 is sufficient.
therefore the answer is D
Hope the solution is clear.
_________________

--It's one thing to get defeated, but another to accept it.

Intern
Joined: 17 Jun 2014
Posts: 27
Location: India
WE: Information Technology (Computer Software)
If a certain culture of bacteria [#permalink]

### Show Tags

08 Sep 2014, 13:40
1
This post was
BOOKMARKED
If a certain culture of bacteria increases by a factor of x every y minutes, how long will it take for the culture to increase to 10000 times its original amount ?
1) (x)^1/y = 10
2) In 2 minutes the culture will increase to 100 times its original amount.

Please could you explain an how to solve such questions which involves population increasing by certain factors
Director
Joined: 25 Apr 2012
Posts: 727
Location: India
GPA: 3.21
WE: Business Development (Other)
Re: If a certain culture of bacteria [#permalink]

### Show Tags

08 Sep 2014, 20:45
1
KUDOS
ankitaprsd wrote:
If a certain culture of bacteria increases by a factor of x every y minutes, how long will it take for the culture to increase to 10000 times its original amount ?
1) (x)^1/y = 10
2) In 2 minutes the culture will increase to 100 times its original amount.

Please could you explain an how to solve such questions which involves population increasing by certain factors

Stem 1 is interesting..

Consider x=10 and y=1...so Initial bacteria (K) will increase by a factor of 10 in 1 minute...so after 1 minute there will be K+10K=11K...so we can find the time it will take for culture to increase to 10000 times

So after 1 minute, we have 11K
After 2 minutes, 11K+110K=121K
After 3 minutes= 121K+1210K=1331K
After 4 minutes...

Consider $$x=\sqrt{10}$$, and y =1/2 or 30 seconds, So after 30 seconds, no. of bacteria will increase by $$(10^{1/2})^{2}$$ or by a factor of 10...in 1 minute it will increase by factor $$\sqrt{10}$$
At 0 seconds=K
After 30 seconds= K+10K=11K
After 1 minute, by a factor$$\sqrt{10}$$ so after 1 minute you will have $$11K+\sqrt{10}*11K$$-----> Now here the problem is the increase every y minute is not the same so this case will not be considered...

So St1 is sufficient

St2 is straight forward...

Can you post the Official Explanation to question.
_________________

“If you can't fly then run, if you can't run then walk, if you can't walk then crawl, but whatever you do you have to keep moving forward.”

Math Expert
Joined: 02 Sep 2009
Posts: 39589
Re: If a certain culture of bacteria increases by a constant [#permalink]

### Show Tags

09 Sep 2014, 06:49
ankitaprsd wrote:
If a certain culture of bacteria increases by a factor of x every y minutes, how long will it take for the culture to increase to 10000 times its original amount ?
1) (x)^1/y = 10
2) In 2 minutes the culture will increase to 100 times its original amount.

Please could you explain an how to solve such questions which involves population increasing by certain factors

Merging topics. Please search before posting. Thank you.
_________________
Math Expert
Joined: 02 Sep 2009
Posts: 39589
Re: If a certain culture of bacteria increases by a constant [#permalink]

### Show Tags

09 Sep 2014, 06:50
1
KUDOS
Expert's post
3
This post was
BOOKMARKED
Bunuel wrote:
ankitaprsd wrote:
If a certain culture of bacteria increases by a factor of x every y minutes, how long will it take for the culture to increase to 10000 times its original amount ?
1) (x)^1/y = 10
2) In 2 minutes the culture will increase to 100 times its original amount.

Please could you explain an how to solve such questions which involves population increasing by certain factors

Merging topics. Please search before posting. Thank you.

Similar questions to practice:
a-certain-bacteria-colony-doubles-in-size-every-day-for-144013.html
it-takes-30-days-to-fill-a-laboratory-dish-with-bacteria-140269.html
the-number-of-water-lilies-on-a-certain-lake-doubles-every-142858.html
the-population-of-locusts-in-a-certain-swarm-doubles-every-90353.html
the-population-of-a-bacteria-culture-doubles-every-2-minutes-167378.html
_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15918
Re: If a certain culture of bacteria increases by a constant [#permalink]

### Show Tags

20 Mar 2016, 03:00
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 Legend
Joined: 09 Sep 2013
Posts: 15918
Re: If a certain culture of bacteria increases by a constant [#permalink]

### Show Tags

19 May 2017, 05:27
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.
_________________
Re: If a certain culture of bacteria increases by a constant   [#permalink] 19 May 2017, 05:27
Similar topics Replies Last post
Similar
Topics:
1 Did the quantity of bacteria in an experiment increase by at 2 29 Oct 2012, 14:16
35 The number of antelope in a certain herd increases every 27 23 Jul 2016, 00:45
4 The net value of a certain stock increased at a constant 4 11 Jun 2014, 01:42
1 By what percent will the bacteria population increase in 1 5 29 May 2017, 23:20
10 The price of a certain property increased by 10% in the 8 12 Jun 2016, 12:25
Display posts from previous: Sort by

# If a certain culture of bacteria increases by a constant

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

 Powered by phpBB © phpBB Group and phpBB SEO 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®.