During a trip, F traveled x% of the total distance at an avg speed of 40 km/hr and the rest of the distance at an avg of 60 km/hr. In terms of x, what was F's avg speed for the trip
a. (180-x)/2
b. (x+60)/4
c. (300-x)/5
d. 600/(115-x)
e. 12000/(x+200)
OA E
I tried to solve it using assumption. Please point out my mistake
Let the distance be 480 and let 25% (This is x) of 480 be traveled at 40km/hr and the rest at 60 km/hr
So dist traveled at 40 = 120. Therefore time = 3hrs
Dist traveled at 60 = 360. Therefore time = 6 hrs
Avg speed = 480/9 = 160/3
Then I put x = 25 in all options
My answer didn't match any of the choices.
E= 12000/(25+200) = 12000/225 = 800/9
Please help
Regards,
Vishal
During a trip, F traveled x% of the total distance
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Last edited by vishal.pathak on Thu Mar 08, 2012 8:34 am, edited 1 time in total.
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Almost there, Vishal!vishal.pathak wrote:During a trip, F traveled x% of the total distance at an avg speed of 40 km/hr and the rest of the distance at an avg of 60 km/hr. In terms of x, what was F's avg speed for the trip
a. (180-x)/2
b. (x+60)/4
c. (300-x)/5
d. 600/(115-x)
e. 12000/(x+200)
OA E
I tried to solve it using assumption. Please point out my mistake
Let the distance be 480 and let 25% (This is x) of 480 be traveled at 40km/hr and the rest at 60 km/hr
So dist traveled at 40 = 120. Therefore time = 3hrs
Dist traveled at 60 = 360. Therefore time = 6 hrs
Avg speed = 480/9 = 160/3
Then I put x = 25 in all options
My answer didn't match any of the choices.
[spoiler]E= 12000/(25+200) = 12000/225 = 800/9
[/spoiler]
Please help
Regards,
Vishal
You had the correct answer right up until the end (see above, behind the spoiler).
To simplify 12000/225, we can first divide top and bottom by 25 to get: 480/9, which equals 160/3
Cheers,
Brent
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- Master | Next Rank: 500 Posts
- Posts: 176
- Joined: Thu Sep 22, 2011 5:32 am
- Thanked: 5 times
I am very very stupid. I wish that I dont make such mistakes in the exam. Thanks for your help BrentBrent@GMATPrepNow wrote:Almost there, Vishal!vishal.pathak wrote:During a trip, F traveled x% of the total distance at an avg speed of 40 km/hr and the rest of the distance at an avg of 60 km/hr. In terms of x, what was F's avg speed for the trip
a. (180-x)/2
b. (x+60)/4
c. (300-x)/5
d. 600/(115-x)
e. 12000/(x+200)
OA E
I tried to solve it using assumption. Please point out my mistake
Let the distance be 480 and let 25% (This is x) of 480 be traveled at 40km/hr and the rest at 60 km/hr
So dist traveled at 40 = 120. Therefore time = 3hrs
Dist traveled at 60 = 360. Therefore time = 6 hrs
Avg speed = 480/9 = 160/3
Then I put x = 25 in all options
My answer didn't match any of the choices.
[spoiler]E= 12000/(25+200) = 12000/225 = 800/9
[/spoiler]
Please help
Regards,
Vishal
You had the correct answer right up until the end (see above, behind the spoiler).
To simplify 12000/225, we can first divide top and bottom by 25 to get: 480/9, which equals 160/3
Cheers,
Brent
Regards,
Vishal
GMAT/MBA Expert
- Brent@GMATPrepNow
- GMAT Instructor
- Posts: 16207
- Joined: Mon Dec 08, 2008 6:26 pm
- Location: Vancouver, BC
- Thanked: 5254 times
- Followed by:1268 members
- GMAT Score:770
This is the best time to make silly mistakes. You can get them all out of your system before test dayvishal.pathak wrote: I am very very stupid. I wish that I dont make such mistakes in the exam. Thanks for your help Brent
Regards,
Vishal
Cheers,
Brent