Time, Speed and Distance Questions

Multiple choice
  1. $1000$ metres
  2. $1200$ metres
  3. $1600$ metres
  4. $2000$ metres
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Relative speed = 9 - 8 = 1 km/hr = 1000/3600 m/s = 5/18 m/s. Time to catch = distance / relative speed = 200 / (5/18) = 720 seconds. Distance run by thief = speed * time = (8 * 1000 / 3600) * 720 = (80/36) * 720 = 80 * 20 = 1600 meters.

Multiple choice
  1. After $4$ hours at a distance of $325$ km from station $P$
  2. After $7$ hours at a distance of $385$ km from station $P$
  3. After $5$ hours at a distance of $295$ km from station $P$
  4. After $8$ hours at a distance of $345$ km from station $P$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Relative speed = 55 + 25 = 80 km/hr. Time to meet = Distance / Relative speed = 560 / 80 = 7 hours. Distance from station P = Speed of train P * Time = 55 * 7 = 385 km.

Multiple choice
  1. $35$ km/hr
  2. $20$ km/hr
  3. $65$ km/hr
  4. $50$ km/hr
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Distance 1 = 3 * 40 = 120 km. Distance 2 = 4.5 * 60 = 270 km. Total covered = 390 km. This is 3/5 of total, so total = 390 * 5/3 = 650 km. Remaining = 650 - 390 = 260 km. Speed = 260 / 4 = 65 km/hr.

Multiple choice
  1. $\displaystyle 17 \dfrac{6}{7}$ km/hr
  2. $25$ km/hr
  3. $30$ km/hr
  4. $35$ km/hr
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Time = 1h 40m 48s = 1 + 40/60 + 48/3600 = 1 + 2/3 + 2/150 = 1 + 100/150 + 2/150 = 1 + 102/150 = 1.68 hours. Speed = Distance / Time = 42 / 1.68 = 25 km/hr. This is 5/7 of the usual speed. Usual speed = 25 * 7/5 = 35 km/hr.

Multiple choice
  1. $300$ m
  2. $350$ m
  3. $400$ m
  4. $450$ m
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Relative speed = 10 - 8 = 2 km/hr = 2 * (5/18) m/s = 5/9 m/s. Time to overtake = 100 / (5/9) = 180 seconds. Distance thief runs = 8 km/hr * (180/3600) hr = 8 * (1/20) = 0.4 km = 400 m.

Multiple choice
  1. $420$ km
  2. $480$ km
  3. $640$ km
  4. None of these

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let distance be D and speed be S. D = 8S. Also, D = (S + 4) * 7.5. Equating the two: 8S = 7.5S + 30. This gives 0.5S = 30, so S = 60 km/hr. The distance D = 8 * 60 = 480 km.