GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 20 May 2019, 00:13

### 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 jogger desires to run a certain course in 1/4 less time than she usu

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

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 55172
A jogger desires to run a certain course in 1/4 less time than she usu  [#permalink]

### Show Tags

22 Feb 2018, 20:39
00:00

Difficulty:

35% (medium)

Question Stats:

73% (01:44) correct 27% (01:28) wrong based on 99 sessions

### HideShow timer Statistics

A jogger desires to run a certain course in 1/4 less time than she usually takes. By what percent must she increase her average running speed to accomplish this goal?

(A) 20%

(B) 25%

(C) 33 1/3%

(D) 50%

(E) 75%

_________________
Senior PS Moderator
Joined: 26 Feb 2016
Posts: 3386
Location: India
GPA: 3.12
A jogger desires to run a certain course in 1/4 less time than she usu  [#permalink]

### Show Tags

22 Feb 2018, 22:25
Bunuel wrote:
A jogger desires to run a certain course in 1/4 less time than she usually takes. By what percent must she increase her average running speed to accomplish this goal?

(A) 20%

(B) 25%

(C) 33 1/3%

(D) 50%

(E) 75%

Formula used: Distance = Time*Speed
Let the speed at which she travels be x and the time she takes be t

If the time the jogger takes to complete the course is 1/4 less than she usually takes,
$$\frac{3}{4}t * A = xt$$ -> $$A = \frac{4}{3}*X = (1+\frac{1}{3})X$$

Therefore, the percentage by which the jogger must increase her running speed is $$\frac{1}{3}*100 = 33\frac{1}{3}$$ (Option C)
_________________
You've got what it takes, but it will take everything you've got
Senior Manager
Joined: 31 May 2017
Posts: 326
Re: A jogger desires to run a certain course in 1/4 less time than she usu  [#permalink]

### Show Tags

22 Feb 2018, 23:03
We can find answer quickly by plugging values

Lets say the course is 6 miles and she usually completes the course in 60 Minutes. Now she wants to complete the course in 1/4 less than 60 minutes which is in 45 minutes.

Now if the 6 mile course needs to completed in 1 hour, then the speed needs to be 8 Miles / hour, which is 33.5 % more than original speed.

Ans: C
_________________
Please give kudos if it helps

Resources
| | | | |
Retired Moderator
Joined: 07 Jan 2016
Posts: 1089
Location: India
GMAT 1: 710 Q49 V36
Re: A jogger desires to run a certain course in 1/4 less time than she usu  [#permalink]

### Show Tags

23 Feb 2018, 01:58
Bunuel wrote:
A jogger desires to run a certain course in 1/4 less time than she usually takes. By what percent must she increase her average running speed to accomplish this goal?

(A) 20%

(B) 25%

(C) 33 1/3%

(D) 50%

(E) 75%

let d = 10 t= 60 mins s=10 kmph

d= 10 t =45 mins

speed = 10x4/3 = 13.33

inc = 100/3

(C) imo
Intern
Joined: 30 Sep 2016
Posts: 5
Re: A jogger desires to run a certain course in 1/4 less time than she usu  [#permalink]

### Show Tags

24 Feb 2018, 16:09
Bunuel wrote:
A jogger desires to run a certain course in 1/4 less time than she usually takes. By what percent must she increase her average running speed to accomplish this goal?

(A) 20%

(B) 25%

(C) 33 1/3%

(D) 50%

(E) 75%

Hello Bunuel,

I did it with a different approach but not really sure if it is the proper way to resolve this type of PS. The answer was very close to the one in the answer options. Please let me know what I did wrong.

Let's give some values to the initial time, speed, and distance that she usually takes.

D=S x T 10 =10mph x 60 min. finding S. we have S = D/T therefore S = 10/60min S1= 1/6

Now let use the information given in the argument, however, S and D are the same values. Here the time is 1/4 less than she usually takes. So T = 60 - (60 * 1/4) = 45

D = S X T 10 =10mph x 45 min. we need to find The average speed. So S = D/T therefore S = 10/45min S2= 2/9

Now we have S1=1/6 and S2=2/9.

S1---100%
S2--- X

let's find X: X = (2/9 1/6) X 100 Solution: X = 133.33% Then 133.33% - 100 % = 33.33%
Intern
Status: Current Student
Joined: 27 Mar 2014
Posts: 26
Concentration: Entrepreneurship, Finance
A jogger desires to run a certain course in 1/4 less time than she usu  [#permalink]

### Show Tags

25 Feb 2018, 18:36
1
"Theory: $$X*Y=Z ≈ X(1+\frac{1}{3})*Y(1-\frac{1}{4})=z ≈ X*\frac{4}{3}*Y*\frac{3}{4}=z ≈ X*Y=Z$$

So, increasing one element of a product by $$33 \frac{1}{3}$$% and decreasing another by 25% do not affect the result at all. Basically the same thing as doubling one and halving another."

R*T=D ; If T to decrease by 25% then R must increase by $$33 \frac{1}{3}$$%. Answer: C

NB: The same goes for a 25% increase and a 20% decrease.
Non-Human User
Joined: 09 Sep 2013
Posts: 10948
Re: A jogger desires to run a certain course in 1/4 less time than she usu  [#permalink]

### Show Tags

10 Mar 2019, 00:40
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: A jogger desires to run a certain course in 1/4 less time than she usu   [#permalink] 10 Mar 2019, 00:40
Display posts from previous: Sort by

# A jogger desires to run a certain course in 1/4 less time than she usu

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

 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®.