CFAT Problem Solving: Time/Rate 3 — Questions and Answers
Question 1: At 72 km/h, how many seconds does it take a vehicle to travel 200 metres?
- 8 seconds
- 10 seconds (Correct answer)
- 12 seconds
- 15 seconds
Correct answer: 10 seconds
72 km/h = 20 m/s; time = 200 ÷ 20 = 10 seconds.
Question 2: Worker A completes a task in 6 hours; Worker B takes 9 hours. After working together for 2 hours, A leaves. How long does B take to finish alone?
- 3 hours
- 4 hours (Correct answer)
- 5 hours
- 6 hours
Correct answer: 4 hours
Together rate = 1/6 + 1/9 = 5/18 per h; in 2 h: 10/18 = 5/9 done; remaining = 4/9; B time = (4/9) ÷ (1/9) = 4 hours.
Question 3: A patrol boat travels upstream at 18 km/h and downstream at 30 km/h. What is the speed of the current?
- 4 km/h
- 6 km/h (Correct answer)
- 8 km/h
- 12 km/h
Correct answer: 6 km/h
Current speed = (downstream − upstream) ÷ 2 = (30 − 18) ÷ 2 = 6 km/h.
Question 4: A soldier can run a route in 40 minutes. If he increases his speed by 25%, how long will the same route take?
- 28 min
- 30 min
- 32 min (Correct answer)
- 35 min
Correct answer: 32 min
New speed = 1.25 × old speed; since time is inversely proportional, new time = 40 ÷ 1.25 = 32 minutes.
Question 5: Two aircraft leave the same base simultaneously flying in opposite directions at 500 km/h and 700 km/h. How far apart are they after 90 minutes?
- 1,500 km
- 1,800 km (Correct answer)
- 1,950 km
- 2,100 km
Correct answer: 1,800 km
Combined speed = 1,200 km/h; 90 min = 1.5 h; distance = 1,200 × 1.5 = 1,800 km.
Question 6: A tank can be filled by Pipe X in 4 hours and drained by Pipe Y in 6 hours. If both are open simultaneously, how long to fill the empty tank?
- 8 hours
- 10 hours
- 12 hours (Correct answer)
- 14 hours
Correct answer: 12 hours
Net rate = 1/4 − 1/6 = 1/12 tank per hour; time = 12 hours.
Question 7: A vehicle uses 8 litres per 100 km. Traveling at 80 km/h, how long can it run on a full 48-litre tank?
- 5.5 hours
- 6 hours
- 6.5 hours
- 7.5 hours (Correct answer)
Correct answer: 7.5 hours
Range = (48 ÷ 8) × 100 = 600 km; time = 600 ÷ 80 = 7.5 hours.
CFAT Problem Solving: Time/Rate 3
At 72 km/h, how many seconds does it take a vehicle to travel 200 metres?