SDT Practice DS SET – 1
DS: Speed, Distance & Time – Level 1
Directions: Choose the correct option (A-E) based on sufficiency.
1.
How long did it take a car to travel a certain distance?
(1) The car traveled at an average speed of 50 miles per hour.
(2) The distance traveled was 200 miles.
(1) The car traveled at an average speed of 50 miles per hour.
(2) The distance traveled was 200 miles.
Solution (C):
To find Time, we need Distance and Speed ($T = D/R$).
(1) Gives Rate (50 mph) but no Distance. Not sufficient.
(2) Gives Distance (200 miles) but no Rate. Not sufficient.
Combined: $T = 200 / 50 = 4$ hours. Sufficient.
2.
What was the average speed of a runner for the entire race?
(1) The runner completed the first half of the race in 30 minutes.
(2) The runner completed the second half of the race in 40 minutes.
(1) The runner completed the first half of the race in 30 minutes.
(2) The runner completed the second half of the race in 40 minutes.
Solution (E):
Average Speed = Total Distance / Total Time.
(1) Gives time for first half. No distance.
(2) Gives time for second half. No distance.
Combined: Total Time = 70 minutes. However, we still do not know the **Distance** of the race. It could be a 5k or a marathon. Not sufficient.
3.
Is the speed of Train A greater than 60 mph?
(1) Train A travels 100 miles in less than 2 hours.
(2) Train A travels 120 miles in exactly 1.5 hours.
(1) Train A travels 100 miles in less than 2 hours.
(2) Train A travels 120 miles in exactly 1.5 hours.
Solution (B):
(1) $100 / t > 50$ (since $t < 2$). Speed could be 51 mph (No) or 70 mph (Yes). Not sufficient.
(2) Speed = $120 / 1.5 = 80$ mph. Is 80 > 60? Yes. Sufficient.
4.
Did the cyclist travel more than 30 miles?
(1) The cyclist traveled for 3 hours at a speed greater than 11 mph.
(2) The cyclist traveled for 3 hours at a speed less than 15 mph.
(1) The cyclist traveled for 3 hours at a speed greater than 11 mph.
(2) The cyclist traveled for 3 hours at a speed less than 15 mph.
Solution (A):
(1) Distance > $3 \times 11 = 33$ miles. Since 33 > 30, the answer is definitively Yes. Sufficient.
(2) Distance < $3 \times 15 = 45$ miles. Distance could be 40 (Yes) or 10 (No). Not sufficient.
5.
A train crosses a pole in 10 seconds. What is the speed of the train?
(1) The train crosses a 200m platform in 20 seconds.
(2) The train is 200 meters long.
(1) The train crosses a 200m platform in 20 seconds.
(2) The train is 200 meters long.
Solution (D):
Let length = $L$, Speed = $S$. From prompt: $S = L/10$.
(1) $S = (L+200)/20$. We have two equations: $L/10 = (L+200)/20 \implies 2L = L+200 \implies L=200$. Then $S=20$. Sufficient.
(2) $L = 200$. Since $S = L/10$, $S = 200/10 = 20$. Sufficient.
Answer is D.
Score: 0 / 0