Problem Solving

Hi AAPL,

We're told that Luke drives the first 300 miles of a trip at 60 miles an hour. We're asked how fast he has to drive, in miles per hour, on the final 200 miles of the trip if the total time of the trip is to equal 7 hours. This is an example of a multi-step rate question - and as long as you're organized with your work, the math itself is not that difficult.

For the first part of the trip, we know Luke's speed and distance, so we can figure out the time traveled:
D = (R)(T)
300 = (60 miles/hr)(T)
300/60 = T
5 hours = T

The TOTAL time for the entire trip is supposed to be 7 hours, so Luke has just 7 - 5 = 2 hours for the second part of the trip. With a distance of 200 miles, Luke will have to travel....

200 miles/2 hours = 100 miles/ hour for the second part of the trip.

Final Answer: C

GMAT assassins aren't born, they're made,
Rich

AAPL wrote:Magoosh

Luke drives the first 300 miles of a trip at 60 miles an hour. How fast does he have to drive, in miles per hour, on the final 200 miles of the trip if the total time of the trip is to equal 7 hours?

A. 60 mph
B. 90 mph
C. 100 mph
D. 120 mph
E. 200 mph

OA C

The time for the first part of the trip is 300/60 = 5 hours. Thus, he has 7 - 5 = 2 hours to drive 200 miles. In order to achieve this, he has to drive at 200/2 = 100 mph.

Answer: C

AAPL wrote:Magoosh

Luke drives the first 300 miles of a trip at 60 miles an hour. How fast does he have to drive, in miles per hour, on the final 200 miles of the trip if the total time of the trip is to equal 7 hours?

A. 60 mph
B. 90 mph
C. 100 mph
D. 120 mph
E. 200 mph

OA C

Luke drives the first 300 miles of a trip at 60 miles an hour.
Time = distance/time
So, travel time = 300/60 = 5 hours

How fast does he have to drive, in miles per hour, on the final 200 miles of the trip if the total time of the trip is to equal 7 hours?
Luke has already spent 5 hours driving the first 300 miles.
In order to complete the trip in a TOTAL of 7 hours, Luke must complete the next 200 miles in 2 hours

Speed = distance/ time
So the speed needed for the second leg = 200/2 = 100 mph

Answer: C

Cheers,
Brent