|
Author |
Message |
|
CEO
Joined: 21 Jan 2007
Posts: 2797
Location: New York City
Followers: 5
Kudos [?]:
132
[0], given: 4
|
Question Stats:
44% (01:55) correct
55% (00:55) wrong based on 2 sessions
A plane takes off from a hill at 750 meters above sea level and lands some time later in a town located at 50 meters below sea level. During the first part of its flight, the plane gained height at a rate of 50 meters per minute but then it started to descend at a rate of 20 meters per minute. The duration of the first part of the flight was what percent of the total flight time? 1. The duration of the descent is known. 2. The total flight time is known. Source: GMAT Club Tests - hardest GMAT questions
|
|
|
|
|
|
|
|
|
Senior Manager
Joined: 01 Sep 2006
Posts: 308
Location: Phoenix, AZ, USA
Followers: 1
Kudos [?]:
4
[0], given: 0
|
bmwhype2 wrote: a plane takes off from a hill at 750 meters above sea level and lands some time later in a town located at 50 meters below sea level. During the first part of its flight the plane gained height at 50 meters per minute but then it descended at a rate of 20 meters per minute. The duration of the first part of the flight was what percent of the total flight time?
1. during of descent is known
2. total flgiht time is known
(1) Duration of decent will let us know the highest point the plane was at.
So by sybstracting 750 from highest point we know how much it climed in acent. So we can figure out time for ascent. Thus we can calcuate ratio
Suff
2 Insuff
|
|
|
|
|
|
CEO
Joined: 17 Nov 2007
Posts: 3594
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 231
Kudos [?]:
1300
[0], given: 346
|
D
general equation: 750-50=20*td-50ta ==> 2*td-5*ta=70
where ta - time of ascent, td - time of descent
1. we know td. we can find ta from general equation. SUFF.
2. we know ta+td. we can solve system of 2 equations. SUFF.
|
|
|
|
|
|
Intern
Joined: 15 Dec 2008
Posts: 20
Schools: anything
Followers: 0
Kudos [?]:
4
[0], given: 3
|
walker wrote: D
general equation: 750-50=20*td-50ta ==> 2*td-5*ta=70
where ta - time of ascent, td - time of descent
1. we know td. we can find ta from general equation. SUFF.
2. we know ta+td. we can solve system of 2 equations. SUFF. Thx... I was wondering why it was 750+50 in explanation..
|
|
|
|
|
|
CEO
Joined: 29 Aug 2007
Posts: 2530
Followers: 41
Kudos [?]:
358
[1] , given: 19
|
Re: ds rate (m08q34) [#permalink]
 15 Oct 2009, 23:23
1
This post received
KUDOS
bmwhype2 wrote: A plane takes off from a hill at 750 meters above sea level and lands some time later in a town located at 50 meters below sea level. During the first part of its flight, the plane gained height at a rate of 50 meters per minute but then it started to descend at a rate of 20 meters per minute. The duration of the first part of the flight was what percent of the total flight time?
1. The duration of the descent is known.
2. The total flight time is known. mandb wrote: walker wrote: D
general equation: 750-50=20*td-50ta ==> 2*td-5*ta=70
where ta - time of ascent, td - time of descent
1. we know td. we can find ta from general equation. SUFF.
2. we know ta+td. we can solve system of 2 equations. SUFF. Thx... I was wondering why it was 750+50 in explanation.. It is. Present height + (+ accent) - (- level below the sea) = 20d 750 + 50a - (-50) = 20d 75 + 5a + 5 = 2d 80 + 5a = 2d St. 1) The duration of the descent (i.e. d) is known. Say d = 50, a = 4. SUFF... St. 2) The total flight (i.e. a+d) time is known. For simplicity, say a+d = 54 a = 54 - d Then, 80 + 5(54-d) = 2d. d = 50. SUFF. D
_________________
Verbal: new-to-the-verbal-forum-please-read-this-first-77546.html
Math: new-to-the-math-forum-please-read-this-first-77764.html
Gmat: everything-you-need-to-prepare-for-the-gmat-revised-77983.html
GT
|
|
|
|
|
|
Intern
Joined: 15 Dec 2008
Posts: 20
Schools: anything
Followers: 0
Kudos [?]:
4
[0], given: 3
|
Re: ds rate (m08q34) [#permalink]
16 Oct 2009, 16:47
GMAT TIGER wrote: bmwhype2 wrote: A plane takes off from a hill at 750 meters above sea level and lands some time later in a town located at 50 meters below sea level. During the first part of its flight, the plane gained height at a rate of 50 meters per minute but then it started to descend at a rate of 20 meters per minute. The duration of the first part of the flight was what percent of the total flight time?
1. The duration of the descent is known.
2. The total flight time is known. mandb wrote: walker wrote: D
general equation: 750-50=20*td-50ta ==> 2*td-5*ta=70
where ta - time of ascent, td - time of descent
1. we know td. we can find ta from general equation. SUFF.
2. we know ta+td. we can solve system of 2 equations. SUFF. Thx... I was wondering why it was 750+50 in explanation.. It is. Present height + (+ accent) - (- level below the sea) = 20d 750 + 50a - (-50) = 20d 75 + 5a + 5 = 2d 80 + 5a = 2d St. 1) The duration of the descent (i.e. d) is known. Say d = 50, a = 4. SUFF... St. 2) The total flight (i.e. a+d) time is known. For simplicity, say a+d = 54 a = 54 - d Then, 80 + 5(54-d) = 2d. d = 50. SUFF. D Oh I see one is above sea level and other one is below 
|
|
|
|
|
|
Senior Manager
Affiliations: SPG
Joined: 15 Nov 2006
Posts: 327
Followers: 9
Kudos [?]:
180
[3] , given: 19
|
Re: ds rate (m08q34) [#permalink]
07 Jun 2010, 10:53
3
This post received
KUDOS
bmwhype2 wrote: A plane takes off from a hill at 750 meters above sea level and lands some time later in a town located at 50 meters below sea level. During the first part of its flight, the plane gained height at a rate of 50 meters per minute but then it started to descend at a rate of 20 meters per minute. The duration of the first part of the flight was what percent of the total flight time?
1. The duration of the descent is known.
2. The total flight time is known. let duration of ascend = u mins [up]
let duration of descend = d mins [down]
from the information we can write the below equation
50u+20d=800
(1) if d is known, we can calculate u's value
(2) if u+d is known, then we'll have two equations and we can solve them to get u's value
_________________
press kudos, if you like the explanation, appreciate the effort or encourage people to respond.
Download the Ultimate SC Flashcards
|
|
|
|
|
|
Intern
Joined: 27 Jul 2010
Posts: 17
Location: Bangalore
Followers: 0
Kudos [?]:
2
[0], given: 0
|
Re: ds rate (m08q34) [#permalink]
29 Oct 2010, 05:35
dimitri92 wrote: bmwhype2 wrote: A plane takes off from a hill at 750 meters above sea level and lands some time later in a town located at 50 meters below sea level. During the first part of its flight, the plane gained height at a rate of 50 meters per minute but then it started to descend at a rate of 20 meters per minute. The duration of the first part of the flight was what percent of the total flight time?
1. The duration of the descent is known.
2. The total flight time is known. let duration of ascend = u mins [up]
let duration of descend = d mins [down]
from the information we can write the below equation
50u+20d=800
(1) if d is known, we can calculate u's value
(2) if u+d is known, then we'll have two equations and we can solve them to get u's valueI donot understand why vertical height is being considered here. A plane will never travel vertically down. The path followed is the hypotenuse of the triangle formed by the ground distance covered and the vertical height. The descent distance will definitely be greater than the vertical distance. Shouldnt we try to form a triangle to solve this? Plz help me out here.
_________________
Nothing is free.. You 've to earn it!!!
|
|
|
|
|
|
Manager
Status: I rest, I rust.
Joined: 04 Oct 2010
Posts: 128
Schools: ISB - Co 2013
WE 1: IT Professional since 2006
Followers: 13
Kudos [?]:
84
[5] , given: 8
|
Re: ds rate (m08q34) [#permalink]
29 Oct 2010, 06:11
5
This post received
KUDOS
bmwhype2 wrote: A plane takes off from a hill at 750 meters above sea level and lands some time later in a town located at 50 meters below sea level. During the first part of its flight, the plane gained height at a rate of 50 meters per minute but then it started to descend at a rate of 20 meters per minute. The duration of the first part of the flight was what percent of the total flight time? 1. The duration of the descent is known. 2. The total flight time is known. Source: GMAT Club Tests - hardest GMAT questions Say the plane ascended by X meter @ 50mpm and descended (X+750+50) = (X+800) meter @ 20 mpm. Time to go up, Tu = X/50 min ------------------------ eq1 Time to go down, Td = (X+800)/20 min. -------- eq2 Total time, Tt = Tu + Td = (7X+4000)/100 ----------- eq3 1) We have Td. So we can find out X from eq2 and plug in eq1 to get Tu. Sufficient.2) We have Tt. So we can find out X from eq3 and plug in eq1 to get Tu. Sufficient.D
_________________
Respect,
Vaibhav
PS: Correct me if I am wrong.
|
|
|
|
|
|
Manager
Status: I rest, I rust.
Joined: 04 Oct 2010
Posts: 128
Schools: ISB - Co 2013
WE 1: IT Professional since 2006
Followers: 13
Kudos [?]:
84
[0], given: 8
|
Re: ds rate (m08q34) [#permalink]
29 Oct 2010, 06:18
BalakumaranP wrote: dimitri92 wrote: bmwhype2 wrote: A plane takes off from a hill at 750 meters above sea level and lands some time later in a town located at 50 meters below sea level. During the first part of its flight, the plane gained height at a rate of 50 meters per minute but then it started to descend at a rate of 20 meters per minute. The duration of the first part of the flight was what percent of the total flight time?
1. The duration of the descent is known.
2. The total flight time is known. let duration of ascend = u mins [up]
let duration of descend = d mins [down]
from the information we can write the below equation
50u+20d=800
(1) if d is known, we can calculate u's value
(2) if u+d is known, then we'll have two equations and we can solve them to get u's valueI donot understand why vertical height is being considered here. A plane will never travel vertically down. The path followed is the hypotenuse of the triangle formed by the ground distance covered and the vertical height. The descent distance will definitely be greater than the vertical distance. Shouldnt we try to form a triangle to solve this? Plz help me out here. If the plane took T mins to reach from height X to ground, no matter what horizontal distance it covered, it would still have taken T mins to reach from hieght X to height 0. Consider this on coordinate plane XY. Say the plane was initially at (1,10) and it took T min to reach (X,0). Now it matters not what the value of X is, since we know that displacement of body from Y=10 from Y=0 happened in T mins. Makes sense??
_________________
Respect,
Vaibhav
PS: Correct me if I am wrong.
|
|
|
|
|
|
Manager
Status: I rest, I rust.
Joined: 04 Oct 2010
Posts: 128
Schools: ISB - Co 2013
WE 1: IT Professional since 2006
Followers: 13
Kudos [?]:
84
[0], given: 8
|
Re: ds rate (m08q34) [#permalink]
29 Oct 2010, 06:35
mandb wrote: Oh I see one is above sea level and other one is below Thats the beauty of DS. Even if you'd incorrectly assumed both were ABOVE sea level, you'd still have been able to answer the question.
_________________
Respect,
Vaibhav
PS: Correct me if I am wrong.
|
|
|
|
|
|
Intern
Joined: 27 Jul 2010
Posts: 17
Location: Bangalore
Followers: 0
Kudos [?]:
2
[1] , given: 0
|
Re: ds rate (m08q34) [#permalink]
29 Oct 2010, 07:08
1
This post received
KUDOS
Yes.. now I get it.. The slope of the path taken upward and downward are perpendicular. Assuming this, we need not consider the horizontal distance covered.
_________________
Nothing is free.. You 've to earn it!!!
|
|
|
|
|
|
Manager
Joined: 16 Feb 2010
Posts: 236
Followers: 2
Kudos [?]:
22
[0], given: 16
|
Re: ds rate (m08q34) [#permalink]
29 Oct 2010, 07:46
bmwhype2 wrote: A plane takes off from a hill at 750 meters above sea level and lands some time later in a town located at 50 meters below sea level. During the first part of its flight, the plane gained height at a rate of 50 meters per minute but then it started to descend at a rate of 20 meters per minute. The duration of the first part of the flight was what percent of the total flight time? 1. The duration of the descent is known. 2. The total flight time is known. Source: GMAT Club Tests - hardest GMAT questions IMO this question is wrongly worded. By asking for the %, the answer should be sufficient if only we are able to give a number back.... therefore IMO rephrase the question or give some numbers to (1) and (2) the question allows the answer to be different values...different values mean different answers therefore insufficient statements
|
|
|
|
|
|
Manager
Status: I rest, I rust.
Joined: 04 Oct 2010
Posts: 128
Schools: ISB - Co 2013
WE 1: IT Professional since 2006
Followers: 13
Kudos [?]:
84
[0], given: 8
|
Re: ds rate (m08q34) [#permalink]
29 Oct 2010, 08:06
zisis wrote: bmwhype2 wrote: A plane takes off from a hill at 750 meters above sea level and lands some time later in a town located at 50 meters below sea level. During the first part of its flight, the plane gained height at a rate of 50 meters per minute but then it started to descend at a rate of 20 meters per minute. The duration of the first part of the flight was what percent of the total flight time? 1. The duration of the descent is known. 2. The total flight time is known. Source: GMAT Club Tests - hardest GMAT questions IMO this question is wrongly worded. By asking for the %, the answer should be sufficient if only we are able to give a number back.... therefore IMO rephrase the question or give some numbers to (1) and (2) the question allows the answer to be different values...different values mean different answers therefore insufficient statements I beg to differ. DS questions do not ask us to find the answer, they just ask us whether or not it is possible to find the answer. Agreed, for different values of Descent Time and Total Time we'd get different values, but answer to DS question would always be same "Yes, we can find the answer" or "No, we can not find answer", whichever the case may be.
_________________
Respect,
Vaibhav
PS: Correct me if I am wrong.
|
|
|
|
|
|
Manager
Joined: 16 Feb 2010
Posts: 236
Followers: 2
Kudos [?]:
22
[0], given: 16
|
Re: ds rate (m08q34) [#permalink]
29 Oct 2010, 08:49
vaibhavtripathi wrote: zisis wrote: bmwhype2 wrote: A plane takes off from a hill at 750 meters above sea level and lands some time later in a town located at 50 meters below sea level. During the first part of its flight, the plane gained height at a rate of 50 meters per minute but then it started to descend at a rate of 20 meters per minute. The duration of the first part of the flight was what percent of the total flight time? 1. The duration of the descent is known. 2. The total flight time is known. Source: GMAT Club Tests - hardest GMAT questions IMO this question is wrongly worded. By asking for the %, the answer should be sufficient if only we are able to give a number back.... therefore IMO rephrase the question or give some numbers to (1) and (2) the question allows the answer to be different values...different values mean different answers therefore insufficient statements I beg to differ. DS questions do not ask us to find the answer, they just ask us whether or not it is possible to find the answer. Agreed, for different values of Descent Time and Total Time we'd get different values, but answer to DS question would always be same "Yes, we can find the answer" or "No, we can not find answer", whichever the case may be. : ) i disagree - the DS questions ask if the info is enought to answer the question! the statements are not enough to answer the question! if the statements were sufficient to answer the question, then our answer should be a defined % ! anyone else who would like to contribute to this discusion?
|
|
|
|
|
|
Intern
Joined: 13 Oct 2010
Posts: 26
Followers: 1
Kudos [?]:
8
[0], given: 3
|
Re: ds rate (m08q34) [#permalink]
30 Oct 2010, 19:56
Thanks for the explaination guys.
|
|
|
|
|
|
Manager
Joined: 18 Aug 2010
Posts: 92
Followers: 1
Kudos [?]:
3
[0], given: 22
|
Re: ds rate (m08q34) [#permalink]
02 Feb 2011, 13:58
GMAT TIGER wrote: bmwhype2 wrote: A plane takes off from a hill at 750 meters above sea level and lands some time later in a town located at 50 meters below sea level. During the first part of its flight, the plane gained height at a rate of 50 meters per minute but then it started to descend at a rate of 20 meters per minute. The duration of the first part of the flight was what percent of the total flight time?
1. The duration of the descent is known.
2. The total flight time is known. mandb wrote: walker wrote: D
general equation: 750-50=20*td-50ta ==> 2*td-5*ta=70
where ta - time of ascent, td - time of descent
1. we know td. we can find ta from general equation. SUFF.
2. we know ta+td. we can solve system of 2 equations. SUFF. Thx... I was wondering why it was 750+50 in explanation.. It is.
Present height + (+ accent) - (- level below the sea) = 20d750 + 50a - (-50) = 20d 75 + 5a + 5 = 2d 80 + 5a = 2d St. 1) The duration of the descent (i.e. d) is known. Say d = 50, a = 4. SUFF... St. 2) The total flight (i.e. a+d) time is known. For simplicity, say a+d = 54 a = 54 - d Then, 80 + 5(54-d) = 2d. d = 50. SUFF. D i am still confused with the above highlighted part. can somebody explain? i cant visualize how the distance without considering slope is obtained. something like drawing would be highly appreciated.
|
|
|
|
|
|
Manager
Joined: 27 Apr 2010
Posts: 105
Followers: 0
Kudos [?]:
5
[0], given: 22
|
Re: ds rate (m08q34) [#permalink]
02 Nov 2011, 09:25
Takeaway: Essentially this is a system of eqn or substitution problem 20y = 800 + 50x or 20y - 50x = 800 1) we know y; sufficient 2) a+Y=given; sufficient Try to get one variable. Edit: oops mistype; lol i give up typing on my phone... Posted from my mobile device 
_________________
GOAL: 7xx
Last edited by snkrhed on 02 Nov 2011, 09:38, edited 2 times in total.
|
|
|
|
|
|
Manager
Joined: 27 Apr 2010
Posts: 105
Followers: 0
Kudos [?]:
5
[0], given: 22
|
Re: ds rate (m08q34) [#permalink]
02 Nov 2011, 09:33
tinki wrote: GMAT TIGER wrote:
Present height + (+ accent) - (- level below the sea) = 20d
750 + 50a - (-50) = 20d
75 + 5a + 5 = 2d
80 + 5a = 2d
St. 1) The duration of the descent (i.e. d) is known.
Say d = 50, a = 4. SUFF...
St. 2) The total flight (i.e. a+d) time is known.
For simplicity, say a+d = 54
a = 54 - d
Then, 80 + 5(54-d) = 2d.
d = 50. SUFF.
D
i am still confused with the above highlighted part. can somebody explain? i cant visualize how the distance without considering slope is obtained. something like drawing would be highly appreciated. [/quote] Descent = beginning + ascend / min - ending location Or 20y = 750+50x-(-50) Posted from my mobile device Posted from my mobile device
_________________
GOAL: 7xx
|
|
|
|
|
|
Manager
Joined: 28 Jul 2011
Posts: 118
Followers: 0
Kudos [?]:
1
[0], given: 6
|
Re: ds rate (m08q34) [#permalink]
02 Nov 2011, 10:24
Thanks for explaining.
|
|
|
|
|
|
|
Re: ds rate (m08q34)
[#permalink]
02 Nov 2011, 10:24
|
|
|
|
|
|
|
|
|
|
|
close
