Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 19 Sep 2003
Posts: 158
Location: michigan

The average speed of a car decreased by 3 miles per hour [#permalink]
Show Tags
08 Jan 2005, 14:37
1
This post received KUDOS
14
This post was BOOKMARKED
Question Stats:
68% (03:07) correct
32% (02:37) wrong based on 420 sessions
HideShow timer Statistics
The average speed of a car decreased by 3 miles per hour every successive 8minutes interval. If the car traveled 4.8 miles in the sixth 8minute interval, what was the average speed of the car, in miles per hour, in the first 8 minute interval?
A.35
B.40
C.48
D.51
E.53
Official Answer and Stats are available only to registered users. Register/ Login.



Manager
Joined: 14 Dec 2004
Posts: 117

In the 6th interval, r=d/t = (4.8)*(15/2)=36 mph
Since the rate decreased by 3 mph in each successive interval, in the first it would have been r=51mph.



Manager
Joined: 19 Sep 2003
Posts: 158
Location: michigan

Didn't get it [#permalink]
Show Tags
08 Jan 2005, 15:54
Hello cloaked_vessel:
You got the right answer, but I am not sure how you got to your setup.
Please give me more detail.
THX,
wiseguy



Director
Joined: 07 Jun 2004
Posts: 612
Location: PA

1
This post was BOOKMARKED
Wiseguy hope the below explnation will help you
Let x be the speed at time inteeval 1 so it decreases by 3mph so at 6th its speed is x15
Now in the time span of 8 min it travles 4.8 miles so
speed = 4.8 / ( 8 / 60 ) = 36 mph
But x  15 = 36
x = 51



Current Student
Joined: 29 Jan 2005
Posts: 5218

The average speed of a car decreased by 3 mph every [#permalink]
Show Tags
29 Oct 2005, 09:46
2
This post received KUDOS
8
This post was BOOKMARKED
The average speed of a car decreased by 3 miles per hour every successive 8minute interval. If the car traveled 4.8 miles in the sixth 8minute interval, what was the average speed of the car, in miles per hour, in the first 8minute interval?
A. 35 B. 40 C. 48 D. 51 E. 53
Last edited by Bunuel on 17 Sep 2014, 00:34, edited 1 time in total.
Edited the question.



Manager
Joined: 01 Aug 2005
Posts: 68

Re: The average speed of a car decreased by 3 mph every [#permalink]
Show Tags
29 Oct 2005, 09:58
D. 51
av. speed in 6th interval 36mph
+3 +3 +3 +3 +3 = 51mph in 1st 8 minute interval.



Director
Joined: 24 Oct 2005
Posts: 572
Location: NYC

Re: The average speed of a car decreased by 3 mph every [#permalink]
Show Tags
29 Oct 2005, 18:20
2
This post received KUDOS
51
and here is why.
In the last 6th 8 minute interval he travelled 4.8 miles..
so the average speed in the last 8 minute interval is 4.8/8 = 0.6 miles/minute which is he travles 0.6*60 miles in an hour = 36 miles in an hour
Since this was the 6th 8 minute interval and the speed decreases 3 miles/hr every 8 min, backsolvin it.. 51miles/hr



Manager
Joined: 21 Sep 2005
Posts: 232

Re: The average speed of a car decreased by 3 mph every [#permalink]
Show Tags
30 Oct 2005, 05:52
bewakoof wrote: 51
and here is why. In the last 6th 8 minute interval he travelled 4.8 miles.. so the average speed in the last 8 minute interval is 4.8/8 = 0.6 miles/minute which is he travles 0.6*60 miles in an hour = 36 miles in an hour
Since this was the 6th 8 minute interval and the speed decreases 3 miles/hr every 8 min, backsolvin it.. 51miles/hr
Hmm...man you are NOT bewakoof



Director
Joined: 24 Oct 2005
Posts: 659
Location: London

Re: The average speed of a car decreased by 3 mph every [#permalink]
Show Tags
01 Nov 2005, 09:32
If Original speed is x, in the 6th interval, speed is x15
Time for 6th interval = 8min = 8/60 hrs
Distance = 4.8 mph
D=s*t
4.8 = (x15)8/60.
Solving for x, we get 51 which is original speed.



GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15919

Re: The average speed of a car decreased by 3 mph every [#permalink]
Show Tags
15 Sep 2014, 23:18
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 Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources



Verbal Forum Moderator
Joined: 16 Jun 2012
Posts: 1127
Location: United States

Re: The average speed of a car decreased by 3 mph every [#permalink]
Show Tags
16 Sep 2014, 23:59
1
This post received KUDOS
GMATT73 wrote: The average speed of a car decreased by 3 mph every successive 8 mile interval. If the car traveled 4.8 miles in the 6th 8 minute interval, what was the average speed of the car, in mph, in the first 8 minute interval?
A. 35 B. 40 C. 48 D. 51 E. 53 Hello. The question stem should be corrected. See the red part above. The question says "every successive 8 mile interval". In fact, it should be "every successive 8 MINUTES interval" I'm surprised many folks can solve this question Cheer!
_________________
Please +1 KUDO if my post helps. Thank you.
"Designing cars consumes you; it has a hold on your spirit which is incredibly powerful. It's not something you can do part time, you have do it with all your heart and soul or you're going to get it wrong."
Chris Bangle  Former BMW Chief of Design.



Math Expert
Joined: 02 Sep 2009
Posts: 39597

Re: The average speed of a car decreased by 3 mph every [#permalink]
Show Tags
17 Sep 2014, 00:34



Manager
Joined: 23 Dec 2014
Posts: 51

Re: The average speed of a car decreased by 3 mph every [#permalink]
Show Tags
08 Feb 2015, 17:10
GMATT73 wrote: The average speed of a car decreased by 3 miles per hour every successive 8minute interval. If the car traveled 4.8 miles in the sixth 8minute interval, what was the average speed of the car, in miles per hour, in the first 8minute interval?
A. 35 B. 40 C. 48 D. 51 E. 53 Assume the speed was X in the first 8minute interval So the speed would be x3 after first interval .................... So the speed will be x15 at the 6th interval Now, Rate x Time = Distance (X15) x 8 min = 4.8 miles > (x15) x 8/60 hours = 4.8 miles > X15 = (4.8) x 60/8= 36 > X=36+15= 51 Ans D



GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15919

Re: The average speed of a car decreased by 3 miles per hour [#permalink]
Show Tags
27 Apr 2015, 13:52
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 Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources



EMPOWERgmat Instructor
Status: GMAT Assassin/CoFounder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 9254
Location: United States (CA)
GRE 1: 340 Q170 V170

Re: The average speed of a car decreased by 3 miles per hour [#permalink]
Show Tags
27 Apr 2015, 15:04
Hi All, We're told that a car trip is broken down into 8minute 'intervals'; this is a little 'strange' since we're used to seeing car trips broken down by distances. The math involved is the same though: we're going to use the Distance Formula and do some arithmetic to get to the correct answer. We're told that the SIXTH interval has the car traveling 4.8 miles in 8 minutes... We can use this to figure out the speed of the car during that interval: Distance = (Rate)(Time) 4.8 miles = (R)(8 minutes) 4.8 miles = (R)(8/60 hours) 4.8/(8/60) = R 36 miles/hour = R Now we know that the car was traveling at an average speed of 36 mph in that SIXTH interval. We're told the average speed DECREASES by 3 miles per hour from one interval to the next, so we can work 'backwards' to figure out the speeds at each of the previous intervals. We're asked for the average speed of the car during the FIRST interval... 6th interval = 36mph 5th interval = 39mph 4th interval = 42mph 3rd interval = 45mph 2nd interval = 48mph 1st interval = 51mph Final Answer: GMAT assassins aren't born, they're made, Rich
_________________
760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com
Rich Cohen
CoFounder & GMAT Assassin
***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************



GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15919

Re: The average speed of a car decreased by 3 mph every [#permalink]
Show Tags
19 May 2016, 11:37
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 Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources



Director
Joined: 18 Oct 2014
Posts: 908
Location: United States
GPA: 3.98

Re: The average speed of a car decreased by 3 mph every [#permalink]
Show Tags
19 May 2016, 20:15
Speed in 6th interval= 4.8*60/8= 36 miles/ hr Assume speed in 1st interval is x miles/hr. Then speed in 6th interval will be x15 miles/hr x15=36 x=51 D is the answer
_________________
I welcome critical analysis of my post!! That will help me reach 700+



Verbal Forum Moderator
Joined: 02 Aug 2009
Posts: 4559

Re: The average speed of a car decreased by 3 mph every [#permalink]
Show Tags
19 May 2016, 20:39
wiseguy wrote: The average speed of a car decreased by 3 miles per hour every successive 8minutes interval. If the car traveled 4.8 miles in the sixth 8minute interval, what was the average speed of the car, in miles per hour, in the first 8 minute interval?
A.35 B.40 C.48 D.51 E.53 Hi, another way DEPENDENT on choices..the speed in sixth 8minute interval will be a multiple of 3.. 4.8/6*60..and the reduction in speed was also in multiple of 3.. so the speed in every interval should be multiple of 3.. ONLY D and C are left... Now the multiples of 3 are alternately ODD and EVEN...so SIXinterval means 5 minuses.. so EVEN multiple of 3  ODD(5) multiple of 3.. so ans should be ODD multiple of 3.. ONLY D is left D
_________________
Absolute modulus :http://gmatclub.com/forum/absolutemodulusabetterunderstanding210849.html#p1622372 Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html



Director
Joined: 07 Dec 2014
Posts: 706

Re: The average speed of a car decreased by 3 mph every [#permalink]
Show Tags
14 Jun 2016, 19:40
4.8 miles/(1/7.5 hours)=36 mph 36+5*3=51 mph




Re: The average speed of a car decreased by 3 mph every
[#permalink]
14 Jun 2016, 19:40







