alto34 wrote:Hi,
My answer would be C.
This problem is to be solved with the classic equation: S = D / T
Statement A:
We do not know neither the average speed (S) nor the total time (T) it took her to reach her destination, so we can't calculate the total distance. STATEMENT A alone insuficient
Statement B:
we only know the Speed. So STATEMENT B alone insufficient.
But if we take both statement we can solve the problem.
From statement A we know that :
- it took her 35 minutes (T1) to drive 1/2 D
- the average speed during the second half of the trip (S2) was 50 miles / hour
From statement B we know that :
- the global average speed is 40 miles / hour (S), it is also:
S = (S1 + S2) / 2 where S1 is the speed during the first half of the trip.
40= (S1 + 50) / 2
S1 = 30 miles per/hour
Now we know S1, T1 so we can calculat D1 (wich is equivalent to 1/2 D)
1/2 D = S1 T1
D= 2 * 30 * 7/12
D= 35
So IMO C A and B
Am I right?
:roll: C is right; but you are not!
First thing first: A, B, ..., E are answers; not statements, right? Write (1) or (2) for statements.
Next: Average speed is not the average of speeds.
Average Speed = Total Distance/Total Time. Although, you are not supposed to solve a DS problem till an answer; but when it comes to explanation, it should be precise, agree?
See it again:
What was approximately the total distance in miles Gloria had to drive?
(1) Gloria drove half of her distance in 35 minutes and the remaining half at 50 miles per hour.
(2) Gloria achieved an overall average speed of 40 miles per hour.
Given that each statement alone is not sufficient, we go for merger then.
If 2 d is total distance, in miles, then total time = [(35/60) + (d/50)] hours; and {2 d/[(35/60) + (d/50)]} = 40, would find your d, hence 2 d.
How was that
:
The mind is everything. What you think you become. -Lord Buddha
Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001
www.manyagroup.com
