This is a
Data Sufficiency question. Let's solve it step by step.
Given
- Distance going = 20 miles
- Speed going = 15 mph
- Distance returning = 20 miles
- Return speed = vv, which we need to find.
First, calculate the
time taken going:
t=2015=43 hourst=\frac{20}{15}=\frac43\text{ hours}
The total distance is:
20+20=40 miles20+20=40\text{ miles}
Statement (1): The cyclist took 2 hours for the entire trip.
Total time = 2 hours.
Time going:
43\frac43
Therefore, return time:
2−43=23 hours2-\frac43=\frac23\text{ hours}
Return speed:
v=202/3=30 mphv=\frac{20}{2/3}=30\text{ mph}
So
Statement 1 alone is sufficient. ✅
Statement (2): Average speed for the round trip is 20 mph.
Remember:
Average speed=Total distanceTotal time\text{Average speed}=\frac{\text{Total distance}}{\text{Total time}}
So:
20=40Total time20=\frac{40}{\text{Total time}}
Therefore:
Total time=2 hours\text{Total time}=2\text{ hours}
And we already know that total time of 2 hours allows us to calculate the return speed:
v=30 mphv=30\text{ mph}
So
Statement 2 alone is also sufficient. ✅
Answer
Since
each statement independently gives us enough information:
D — Each statement alone is sufficient\boxed{\text{D — Each statement alone is sufficient}}
Key GMAT trick: Statement (2) gives you the
total time because average speed is based on
total distance ÷ total time, not the simple average of the two speeds.