It is currently 20 Feb 2018, 09:50

Live Now:

Ace the Booth Interview - Live on YouTube

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

A survey was sent to 80 customers, 7 of whom responded. Then the surve

Author Message
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 43831
A survey was sent to 80 customers, 7 of whom responded. Then the surve [#permalink]

Show Tags

18 Nov 2014, 07:29
Expert's post
2
This post was
BOOKMARKED
00:00

Difficulty:

65% (hard)

Question Stats:

58% (01:31) correct 42% (01:17) wrong based on 157 sessions

HideShow timer Statistics

Tough and Tricky questions: Percents.

A survey was sent to 80 customers, 7 of whom responded. Then the survey was redesigned and sent to another 63 customers, 9 of whom responded. By approximately what percent did the response rate increase from the original survey to the redesigned survey?

A. 2%
B. 5%
C. 14%
D. 28%
E. 63%

Kudos for a correct solution.
[Reveal] Spoiler: OA

_________________
Manager
Joined: 10 Sep 2014
Posts: 98
Re: A survey was sent to 80 customers, 7 of whom responded. Then the surve [#permalink]

Show Tags

18 Nov 2014, 07:59
I wrote down (9/63) - (7/80) and then cross multiplied to get 279/5040 which I reduced down to about 6/112 so it looks like there was a 5% difference. Answer B!
Manager
Joined: 21 Jan 2014
Posts: 62
WE: General Management (Non-Profit and Government)
Re: A survey was sent to 80 customers, 7 of whom responded. Then the surve [#permalink]

Show Tags

18 Nov 2014, 20:56
case 1: (7/80)=x/100
x=9%

case 2: (9/63)=y/100
y=14%

So percent increase is =(y-x)=(14-9)%=5%

Intern
Joined: 09 Mar 2014
Posts: 38
Concentration: General Management, Technology
GMAT 1: 650 Q47 V32
GPA: 4
Re: A survey was sent to 80 customers, 7 of whom responded. Then the surve [#permalink]

Show Tags

18 Nov 2014, 21:36
3
KUDOS
Rate of first survey = 7/80
Rate of second survey = 9/63

% Response rate increase (9/63-7/80)/(7/80) = 63%

SVP
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1839
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Re: A survey was sent to 80 customers, 7 of whom responded. Then the surve [#permalink]

Show Tags

18 Nov 2014, 22:57
3
KUDOS

$$\frac{\frac{9}{63} - \frac{7}{80}}{\frac{7}{80}} * 100$$

$$= \frac{31}{560} * \frac{80}{7} * 100 = \frac{3100}{49} \approx{63%}$$
_________________

Kindly press "+1 Kudos" to appreciate

Math Expert
Joined: 02 Sep 2009
Posts: 43831
Re: A survey was sent to 80 customers, 7 of whom responded. Then the surve [#permalink]

Show Tags

19 Nov 2014, 07:02
Official Solution:

A survey was sent to 80 customers, 7 of whom responded. Then the survey was redesigned and sent to another 63 customers, 9 of whom responded. By approximately what percent did the response rate increase from the original survey to the redesigned survey?

A. 2%
B. 5%
C. 14%
D. 28%
E. 63%

To calculate the percent increase of any value, we use this formula: $$\frac{\text{New} - \text{Old}}{\text{Old}}$$. In other words, we subtract the original value $$\text{Old}$$ from the increased value $$\text{New}$$, then divide the result by the original value $$\text{Old}$$. Even though the values themselves may be written using percents, we must be sure to divide by the original value.

In this problem, the original response rate is $$\frac{7}{80}$$. The new response rate is $$\frac{9}{63}$$, or $$\frac{1}{7}$$. The difference is $$\frac{1}{7} - \frac{7}{80}$$. We convert to common denominators: $$\frac{80}{560} - \frac{49}{560} = \frac{31}{560}$$. Now, we divide by the original value, $$\frac{7}{80}$$. Doing so is the same as multiplying by $$\frac{80}{7}$$. This gives us $$\frac{31}{560}*\frac{80}{7} = \frac{31}{49}$$. Estimating, we can see that this fraction is slightly more than $$\frac{30}{50}$$, which is $$\frac{60}{100}$$ or 60%. Thus, the correct answer must be (E): 63%.

Note that the response rates may be written as percents. For instance, the original response rate $$= \frac{7}{80} = 0.0875 = 8.75%$$. Likewise, the new response rate $$= \frac{9}{63} = \frac{1}{7} \approx 14.3%$$. However, if you write these rates this way, do not simply take the difference! That difference, approximately 5 or 6%, does NOT represent the percent increase in the response rate. You must divide by the original response rate.

_________________
Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7942
Location: Pune, India
Re: A survey was sent to 80 customers, 7 of whom responded. Then the surve [#permalink]

Show Tags

06 Apr 2016, 21:30
Bunuel wrote:

Tough and Tricky questions: Percents.

A survey was sent to 80 customers, 7 of whom responded. Then the survey was redesigned and sent to another 63 customers, 9 of whom responded. By approximately what percent did the response rate increase from the original survey to the redesigned survey?

A. 2%
B. 5%
C. 14%
D. 28%
E. 63%

Kudos for a correct solution.

One can use some approximation in such questions:

Initial Response rate = (7/80)* 100 = 7*5/4 = about 9%
Redesigned Response rate = (9/63)* 100 = (1/7)*100 = 14.28% (You should remember these fraction to percent equivalents)

Increase is of about 5 on 9 which is certainly more than 50%. Only (E) satisfies.

_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for \$199

Veritas Prep Reviews

Target Test Prep Representative
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 1975
Re: A survey was sent to 80 customers, 7 of whom responded. Then the surve [#permalink]

Show Tags

26 Jan 2018, 09:36
Bunuel wrote:

Tough and Tricky questions: Percents.

A survey was sent to 80 customers, 7 of whom responded. Then the survey was redesigned and sent to another 63 customers, 9 of whom responded. By approximately what percent did the response rate increase from the original survey to the redesigned survey?

A. 2%
B. 5%
C. 14%
D. 28%
E. 63%

We can use the percent change formula, which is (New - Old)/Old x 100, to determine the percent increase in the response rate:

[(9/63) - (7/80)]/(7/80) x 100 =

[(1/7) - (7/80)]/(7/80) x 100 =

Multiplying the left side by 560/560, we have:

(80 - 49)/49 x 100 =

31/49 x 100

We see that 31/49 is roughly 31/50 = 62/100 = 62%

Alternate Solution:

We can approximate the initial response rate of 7/80 as roughly 7/77, or 1/11. The new response rate is 9 /63, or 1/7. We can use the percent change formula, which is (New - Old)/Old x 100, to determine the percent increase in the response rate:

(1/7 - 1/11)/1/11 x 100 =

Multiplying the expression by 77/77, we obtain:

(11 - 7)/7 x 100 =

4/7 x 100

We see that 4/7 is slightly more than ½, so 4/7 x 100 will be slightly greater than 50%.

_________________

Jeffery Miller

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Re: A survey was sent to 80 customers, 7 of whom responded. Then the surve   [#permalink] 26 Jan 2018, 09:36
Display posts from previous: Sort by