Summer is Coming! Join the Game of Timers Competition to Win Epic Prizes. Registration is Open. Game starts Mon July 1st.

 It is currently 17 Jul 2019, 04:33

### 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

# A quantity increases in a manner such that the ratio of its values in

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

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 56268
A quantity increases in a manner such that the ratio of its values in  [#permalink]

### Show Tags

21 Jun 2019, 00:28
1
8
00:00

Difficulty:

45% (medium)

Question Stats:

60% (02:30) correct 40% (02:15) wrong based on 40 sessions

### HideShow timer Statistics

A quantity increases in a manner such that the ratio of its values in any two consecutive years is constant. If the quantity doubles every 6 years, by what factor does it increase in two years?

A. 4

B. 2

C. $$\sqrt{2}$$

D. $$\sqrt[3]{2}$$

E. $$\frac{1}{2}$$

_________________
ISB School Moderator
Joined: 08 Dec 2013
Posts: 524
Location: India
Concentration: Nonprofit, Sustainability
GMAT 1: 630 Q47 V30
WE: Operations (Non-Profit and Government)
Re: A quantity increases in a manner such that the ratio of its values in  [#permalink]

### Show Tags

21 Jun 2019, 02:28
2
Bunuel wrote:
A quantity increases in a manner such that the ratio of its values in any two consecutive years is constant. If the quantity doubles every 6 years, by what factor does it increase in two years?

A. 4

B. 2

C. $$\sqrt{2}$$

D. $$\sqrt[3]{2}$$

E. $$\frac{1}{2}$$

a, ak, ak^2, ak^3, ak^4, ak^5 and ak^6
Now, ak^6 = 2*a
So, k^6 = 2,

Now required= ak^2/a = k^2
k^6 = 2
=> k^2 = (2)^(1/3)
_________________
Kindly drop a '+1 Kudos' if you find this post helpful.

GMAT Math Book

-I never wanted what I gave up
I never gave up what I wanted-
Manager
Joined: 23 Jul 2015
Posts: 57
Re: A quantity increases in a manner such that the ratio of its values in  [#permalink]

### Show Tags

22 Jun 2019, 16:48
1
Hi!
I used a number to gauge:

Year 1= 100, Year 2= 120, Year 3= 140, Year 4=160, Year 5= 180 and Year 6= 200 (double of Year 1).

120/100= 1.2. I thought the answer was root 2.

Is this the correct method? How did you arrive at cube root 2?
Intern
Status: Chartered Accountant
Joined: 17 Aug 2018
Posts: 16
Location: India
WE: Accounting (Consulting)
Re: A quantity increases in a manner such that the ratio of its values in  [#permalink]

### Show Tags

29 Jun 2019, 04:42
SPatel1992 wrote:
Hi!
I used a number to gauge:

Year 1= 100, Year 2= 120, Year 3= 140, Year 4=160, Year 5= 180 and Year 6= 200 (double of Year 1).

120/100= 1.2. I thought the answer was root 2.

Is this the correct method? How did you arrive at cube root 2?

As per question stem, a quantity increases in a manner such that the ratio of its values in any two consecutive years is constant.

Let's check whether ratio of every two consecutive number in your solution is same or not

Year 1 = 100
Year 2 = 120
Year 3 = 140

Ratio of year 2 to 1 = (value in year 2) / (value in year 1)
= 120/100 = 1.2

Ration of year 3 to 2 = (value in year 3) / (value in year 2)
= 140/120 = 1.6667

Look, ratio of quantity increase in every two consecutive number is not same in the value taken by you; that is because you assumed that increase in the quantity is same every year. It is not anywhere mentioned in the question stem that quantity equally increases every year.

Here, the concept of compounding is used.

Here is the correct answer.
Suppose 1 becomes 2 after 6 years.
let x be the ratio by which 1 increases every year.

value of 1 after 6 years = 1 * (x)^6
so, 2 = 1 *(x)^6
Taking 6th root both side,
2^1/6 = x

So, x = 2^1/6

Value of 1 after 2 years = 1 * (X)^2
Value of 1 after 2 years = 1 * 2^1/6^2
Value of 1 after 2 years = 1 *2^1/3
Value of 1 after 2 years = 2^1/3 (which is third root of 2)

I hope this will be help to you in understanding.

Regards,
Balkrushna Vaghasia
Re: A quantity increases in a manner such that the ratio of its values in   [#permalink] 29 Jun 2019, 04:42
Display posts from previous: Sort by

# A quantity increases in a manner such that the ratio of its values in

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

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne