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how many long hours is the trip

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how many long hours is the trip

by bhumika.k.shah » Sun Jan 31, 2010 2:41 am
A car averages 40 miles per hour for the first 6 hours of a trip and averages 60 miles per hour for each additional hour of travel time. If the average speed for the entire trip is 55 miles per hour, how many hours long is the trip?

A.18
B.20
C.22
D.24
E.26
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by ajith » Sun Jan 31, 2010 2:44 am
bhumika.k.shah wrote:A car averages 40 miles per hour for the first 6 hours of a trip and averages 60 miles per hour for each additional hour of travel time. If the average speed for the entire trip is 55 miles per hour, how many hours long is the trip?

A.18
B.20
C.22
D.24
E.26
Car travels 6*40 =240 Kms in 6 hours

Say the car travels x hours with speed of 60 kmph; the distance travelled = 60x

Now avg speed = total distance / total speed = 60x+240/(x+6) =55

60x +240 = 55x + 330
5x = 90
x = 18

Total trip time = 6+18 = 24 hours
D, IMO
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by bhumika.k.shah » Sun Jan 31, 2010 2:46 am
Thats not the OA
ajith wrote:
bhumika.k.shah wrote:A car averages 40 miles per hour for the first 6 hours of a trip and averages 60 miles per hour for each additional hour of travel time. If the average speed for the entire trip is 55 miles per hour, how many hours long is the trip?

A.18
B.20
C.22
D.24
E.26
Car travels 6*40 =240 Kms in 6 hours

Say the car travels x hours with speed of 60 kmph; the distance travelled = 60x

Now avg speed = total distance / total speed = 60x+240/(x+6) =55

60x +240 = 55x + 330
5x = 90
x = 18

Total trip time = 6+18 = 24 hours
D, IMO
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by kunal_kc » Sun Jan 31, 2010 2:47 am
let additional hours= x

so We get the below equation:

40*6 + 60*x / 6+x = 55

solving for x we get x = 18

hence total journey = 18+6 = 24 hours.
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by bhumika.k.shah » Sun Jan 31, 2010 2:55 am
oops sowree i thought ur answer was 18

Guys OA is D
bhumika.k.shah wrote:Thats not the OA
ajith wrote:
bhumika.k.shah wrote:A car averages 40 miles per hour for the first 6 hours of a trip and averages 60 miles per hour for each additional hour of travel time. If the average speed for the entire trip is 55 miles per hour, how many hours long is the trip?

A.18
B.20
C.22
D.24
E.26
Car travels 6*40 =240 Kms in 6 hours

Say the car travels x hours with speed of 60 kmph; the distance travelled = 60x

Now avg speed = total distance / total speed = 60x+240/(x+6) =55

60x +240 = 55x + 330
5x = 90
x = 18

Total trip time = 6+18 = 24 hours
D, IMO
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by ajith » Sun Jan 31, 2010 3:23 am
bhumika.k.shah wrote:oops sowree i thought ur answer was 18

Guys OA is D
:) No probs... I missed the answer part at first
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