A driver completed the first part of a trip at an average speed of 50

Question

Competition Mode Question

A driver completed the first part of a trip at an average speed of 50 miles per hour and completed the remaining trip at an average speed of 60 miles per hour. What is the average speed for the entire trip?

(1) The first part is 48% of the entire trip.
(2) The distance of the entire trip is 240 miles

(1) The first part is 48% of the entire trip.
(2) The distance of the entire trip is 240 miles

ArunSharma12 · Answer

average speed = total distance/ total time = D1 + D2 / (D1/50 +D2/60)

statement 1:
we get D1 and D2 in terms of D.
D1 is 48% and D2 is 52%.
we'll be able to calculate the average speed.
sufficient

statement 2:
total distance = 240 miles
but we do not know individual distances, so we can not calculate total time taken to complete the distance.
not sufficient

Ans: A

Saasingh · Answer

IMO A.

Let AC be total distance.

_________________________________
A...............B............... C

Avg speed for AB is 50. 
Avg speed for BC is 60.

(1) let total distance is 100d. 
So, AB is 48d and BC is 52d

Avg speed for AC is total distance / totla time = 100d / (48d/50 + 52d/60)

Irrespective of value of d, we get avg speed.

Clearly sufficient.

(2) Total distance is given. 
But we dont know distance for speeds 50 and 60. So we can find the avg speed for entire journey.

Not sufficient.

Posted from my mobile device

MayankSingh · Answer

IMO A

Avg. Speed = Total distance/Total time

First part Avg. speed =50 miles/hr 
Remaining trip avg. speed= 60 miles/hr

(1) The first part is 48% of the entire trip. 
 Total distance = 100D
First part: Speed= 50 Miles/hr , Distance = 48D , Time = 48D/50
Rem Part: Speed= 60 Miles/hr, Disatance = 52D , Time = 52D/60

Avg Speed = 100D/ (48D/50 + 52D/60) = 100/ (48/50 + 52/60)  
 Sufficient.

(2) The distance of the entire trip is 240 miles

Since we won't be able to compute time taken in covering first & second part, we won't be able to compute total time, thus Av.g speed. 
 Not sufficient

yashikaaggarwal · Answer

Average speed for First part of trip = 50miles/hour
Average speed for remaining part of trip = 60miles/hour

Statement 1: The first part is 48% of the entire trip.
48% of distance.
Time taken for first part = 0.48x/50 -----(1)
Time taken for remaining part = 0.52x/60 ------(2)

Average speed for entire trip 
=> x/(0.48x/50)+(0.52x/60)
=> x/(2.88x+2.6x)/300
=> x/(5.48x/300)
=> x*300/5.48x
=> 54.74
(Sufficient)

Statement 2: total distance travel = 240.
(Nothing mentioned regarding first part of remaining part)
(Not sufficient)

IMO A

Posted from my mobile device

exc4libur · Answer

(1) sufic
avg rate: 1/0.48(50)+0.52(60)

(2) insufic
no info about distance or proportion of first part

Ans (A)

HoneyLemon · Answer

Is it A ?

(1) The first part is 48% of the entire trip.

Let total distance is D . 
-----------0.48D in 50 MpH--------------|-------------0.52D in 60 Mph-------------|

Total Avg speed =   \frac{D }{ (0.48D/50) + (0.52D/60)}  
We can find the avg speed . Hence  sufficient  . 
 
(2) The distance of the entire trip is 240 miles

We have no idea about the individual time of each portion .

Hence we cannot deduce the average speed . Insufficient .

Ans is A .

monikakumar · Answer

A driver completed the first part of a trip at an average speed of 50 miles per hour and completed the remaining trip at an average speed of 60 miles per hour. What is the average speed for the entire trip?

(1) The first part is 48% of the entire trip.
(2) The distance of the entire trip is 240 miles

(1) The first part is 48% of the entire trip.
(2) The distance of the entire trip is 240 miles

1) entire trip =x
 avg speed = x/ 
 average speed can be found
 Sufficient

2) time is not known, time for first part of the trip and second part
insufficient

Ans A

GMATinsight · Answer

Question:  Average Speed = \frac{Total-Distance}{Total-Time} =  ?

STatement 1 : The first part is 48% of the entire trip

Let, Total Distance = 100x
First part = 48x
Time to travel first part  = \frac{48x}{50} 
i.e. Second part = 52x
Time to travel Second part  = \frac{52x}{60} 
 Average Speed = \frac{100x}{(48x/50)+(52x/60)} =  Unique value hence

SUFFICIENT

STatement 2 : The distance of the entire trip is 240 miles

SInce we do NOT knopw the ration fo distances tarvelled in first part and second part of the jouney hence

NOT SUFFICIENT

Answer: Option A

bumpbot · Answer

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A driver completed the first part of a trip at an average speed of 50

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