|
Author |
Message |
|
TAGS:
|
|
|
Director
Joined: 30 Nov 2006
Posts: 598
Location: Kuwait
Followers: 8
Kudos [?]:
115
[0], given: 0
|
A boat traveled upstream a distance of 90 miles at an [#permalink]
 01 Jun 2007, 14:04
A boat traveled upstream a distance of 90 miles at an average speed of (v-3) miles per hour and then traveled the same distance downstream at an average speed of (v+3) miles per hour. If the trip upstream took half an hour longer than the trip downstream, how many hours did it take the boat to travel downstram ?
a. 2.5
b. 2.4
c. 2.3
d. 2.2
e. 2.1
I will provide the OA soon.
|
|
|
|
|
|
|
Director
Joined: 30 Nov 2006
Posts: 598
Location: Kuwait
Followers: 8
Kudos [?]:
115
[0], given: 0
|
Yes, but how did you arrive to the answer ? help please
|
|
|
|
|
|
Manager
Joined: 22 May 2007
Posts: 124
Followers: 1
Kudos [?]:
1
[0], given: 0
|
First eq. (v-3)t=90 t-time up the stream
Second eq. (v+3)(t-0.5)=90 - downstream
t=90/(v-3) from first eq.
Plug into the second equation and get v=33
Then t=90/(33-3)=3
time downstream t-30 min or 2 and 1/2 hours
|
|
|
|
|
|
Manager
Joined: 22 May 2007
Posts: 124
Followers: 1
Kudos [?]:
1
[0], given: 0
|
*Note
On the GMAT, I wouldn't try to solve this problem - it would be too time-consuming.
Just start plugging in each answer. If it comes down to solving quadratic equations and stuff like that - you must have taken the wrong approach.
Just my opinion!
|
|
|
|
|
|
Director
Joined: 12 Jun 2006
Posts: 544
Followers: 1
Kudos [?]:
6
[0], given: 1
|
yeah, can/will someone work thru this one?
U
(v-3)(3t/2) = 90
D
(v+3)t=90 => t=90/v+3
When I try to substitute t into (v-3)(3t/2) = 90 it becomes messy.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
close
