During a trip, F traveled x% of the total distance

[vishal.pathak]

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

[Brent@GMATPrepNow]

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

Almost there, 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

[vishal.pathak]

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

Almost there, 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

I am very very stupid. I wish that I dont make such mistakes in the exam. Thanks for your help Brent

Regards,
Vishal

[Brent@GMATPrepNow]

I am very very stupid. I wish that I dont make such mistakes in the exam. Thanks for your help Brent
Regards,
Vishal

This is the best time to make silly mistakes. You can get them all out of your system before test day

Cheers,
Brent