CFAT Problem Solving: Time/Rate 3

Question 1

At 72 km/h, how many seconds does it take a vehicle to travel 200 metres?

Accepted Answer

10 seconds

Answer

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?

Accepted Answer

4 hours

Answer

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?

Accepted Answer

6 km/h

Answer

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?

Accepted Answer

32 min

Answer

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?

Accepted Answer

1,800 km

Answer

Combined speed = 1,200 km/h; 90 min = 1.5 h; distance = 1,200 × 1.5 = 1,800 km.

(CFAT) Canadian Forces Aptitude Test Practice Test