DAA Distance, Speed, and Time Problems 3 — Questions and Answers
Question 1: A car travels the first half of a journey at 60 km/h and the second half at 90 km/h. What is the average speed for the entire journey?
- 70 km/h
- 72 km/h (Correct answer)
- 74 km/h
- 75 km/h
Correct answer: 72 km/h
Average speed = 2 × 60 × 90 ÷ (60 + 90) = 10800 ÷ 150 = 72 km/h.
Question 2: A man rows downstream at 12 km/h and upstream at 6 km/h. What is the speed of the current?
- 2 km/h
- 3 km/h (Correct answer)
- 4 km/h
- 6 km/h
Correct answer: 3 km/h
Current speed = (downstream − upstream) ÷ 2 = (12 − 6) ÷ 2 = 3 km/h.
Question 3: A person travels 40 km in 4 hours on day one and 60 km in 6 hours on day two. What is the average speed over both days combined?
- 8 km/h
- 9 km/h
- 10 km/h (Correct answer)
- 12 km/h
Correct answer: 10 km/h
Total distance = 100 km; total time = 10 hours; average speed = 100 ÷ 10 = 10 km/h.
Question 4: Two cyclists start from opposite ends of a 120 km road at the same time. Cyclist A rides at 20 km/h and Cyclist B at 25 km/h. After how long will they meet?
- 2 hours
- 2 hours 20 minutes
- 2 hours 40 minutes (Correct answer)
- 3 hours
Correct answer: 2 hours 40 minutes
Combined speed = 45 km/h; time = 120 ÷ 45 = 8/3 hours = 2 hours 40 minutes.
Question 5: A boat's speed in still water is 15 km/h and the river current flows at 3 km/h. How long will it take the boat to travel 108 km downstream?
- 5 hours
- 6 hours (Correct answer)
- 7 hours
- 8 hours
Correct answer: 6 hours
Downstream speed = 15 + 3 = 18 km/h; time = 108 ÷ 18 = 6 hours.
Question 6: A military vehicle travels at 80 km/h for 2 hours, then at 60 km/h for 3 hours. What is the total distance covered?
- 260 km
- 300 km
- 320 km
- 340 km (Correct answer)
Correct answer: 340 km
First leg: 80 × 2 = 160 km; second leg: 60 × 3 = 180 km; total = 340 km.
Question 7: A reconnaissance plane flies from base to a target at 600 km/h and returns at 400 km/h. What is the average speed for the round trip?
- 480 km/h (Correct answer)
- 490 km/h
- 500 km/h
- 520 km/h
Correct answer: 480 km/h
Average speed = 2 × 600 × 400 ÷ (600 + 400) = 480000 ÷ 1000 = 480 km/h.
DAA Distance, Speed, and Time Problems 3
A car travels the first half of a journey at 60 km/h and the second half at 90 km/h.
What is the average speed for the entire journey?