BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Speed Distance DS

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 226
Joined: Sun Aug 09, 2009 4:34 am

Speed Distance DS

by ern5231 » Sat Aug 15, 2009 10:24 am
If a car travels a distance of 120 km then what is the average speed of the car?
(1) If the average speed of the car increases by 5 km/hr then the time is reduced by 0.5 hr.
(2) If the average speed is increased by 20%, time will be reduced by 25%.
Top
Source: — Data Sufficiency |
Senior | Next Rank: 100 Posts
Posts: 39
Joined: Sat Jan 03, 2009 11:34 pm

by woo » Sat Aug 15, 2009 9:25 pm
IMO D.

average speed s = total distance travelled d / total time taken t

1) s+5=120/(t-0.5)

2) .2s=120/.85t

Since we also know that s=120/t

we can figure out what s is even with one of the conditions.
Last edited by woo on Mon Aug 17, 2009 6:55 am, edited 1 time in total.
Top
Senior | Next Rank: 100 Posts
Posts: 87
Joined: Sat Feb 28, 2009 7:01 am
Location: India
Thanked: 2 times

by imhimanshu » Sun Aug 16, 2009 3:59 am
IMO A..what is OA?
Top
Master | Next Rank: 500 Posts
Posts: 226
Joined: Sun Aug 09, 2009 4:34 am

by ern5231 » Sun Aug 16, 2009 8:05 pm
OA is A but i would ask for a lil more explanation.

A) Incase of A we get a quadratic equation(check attached pic)

B) My understanding for eliminating B :

120=1.2s*0.75*t
Now, we know s*t=120
120=1.2s*0.75*120/s
which results in cancellation of average speed s throughout so we cannot answer. Is it why we are eliminating this?
Attachments
question.JPG
Top
Master | Next Rank: 500 Posts
Posts: 199
Joined: Mon Apr 06, 2009 4:15 am
Location: India
Thanked: 13 times

by gauravgundal » Sun Aug 16, 2009 11:29 pm
I don't think that the equation would be a Quadratic one.
The distance traveled in both the case will be 120 k.m
For x=avg speed and t- time

120 =x.h
from A
we get,
120=(x+5)(1/2)h
so equating both we get value of x.
so A doesn't leads to a ny Quadratic equation.

Correct me if i am wrong
Top
Post new topic Post Reply
• Page 1 of 1