Time, Speed and Distance Questions

Multiple choice
  1. Quantity A is greater.

  2. Quantity B is greater.

  3. The two quantities are equal.

  4. The relationship cannot be determined from the information given.

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

Alice's average speed = 2 * v1 * v2 / (v1 + v2) = 2 * 15 * 20 / (15 + 20) = 600 / 35 = 17.14 mph. Bob's average speed = Total Distance / Total Time. Let distance be 7d. Bob covers 3d at 15 mph and 4d at 20 mph. Time = 3d/15 + 4d/20 = d/5 + d/5 = 2d/5. Average speed = 7d / (2d/5) = 35/2 = 17.5 mph. Bob's speed is greater.

Multiple choice
  1. 15

  2. 30

  3. 45

  4. 60

  5. a

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

Raj's average speed is the arithmetic mean because he spends equal time at each speed, giving 25 km/h. Vishal's average speed is the harmonic mean because he covers equal distances, giving about 19.2 km/h, so his travel time is about 30% greater.

Multiple choice
  1. Quantity A is greater.

  2. Quantity B is greater.

  3. The two quantities are equal.

  4. The relationship cannot be determined from the information given.

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

Speed of car = 180 / 3 = 60 km/hr. Speed of motorcycle = 180 / 4 = 45 km/hr. Quantity B (60) is greater than Quantity A (45).

Multiple choice
  1. 1

  2. 2

  3. 3

  4. 4

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

Train A starts at 9 am, speed 55. By 10 am, it has traveled 55 km. Remaining distance = 455 - 55 = 400 km. Relative speed = 55 + 45 = 100 kmph. Time to meet = 400 / 100 = 4 hours after 10 am, which is 2 pm.

Multiple choice
  1. 40 kmph

  2. 25 kmph

  3. 30 kmph

  4. 45 kmph

  5. None of these

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

Let v be the boat speed and s=20 be the stream speed. The time ratio (distance/(v-s)) / (distance/(v+s)) = 5/1 simplifies to (v+s)/(v-s) = 5/1. Solving v+20 = 5(v-20) gives v+20 = 5v-100, so 4v = 120 and v = 30 kmph.

Multiple choice
  1. 120 kmph and 60 kmph

  2. 126 kmph and 54 kmph

  3. 130 kmph and 50 kmph

  4. 100 kmph and 50 kmph

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

Let speeds be u and v. When moving towards each other, relative speed is u + v = 360/2 = 180. When moving in the same direction, relative speed is |u - v| = 360/6 = 60. Solving u + v = 180 and u - v = 60 gives u = 120 and v = 60.

Multiple choice
  1. 76

  2. 79

  3. 120

  4. 34

  5. 52

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

Let d be the distance from P to Q, so 200-d is the distance from Q to R. The total time is d/90 + (200-d)/60 = 200/75. Solving this equation, d/90 + (200-d)/60 = 8/3 leads to 2d + 3(200-d) = 480, which simplifies to 600-d = 480, so d = 120.

Multiple choice
  1. 36

  2. 22

  3. 25

  4. 340

  5. 30

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

Total distance = 39 km. Time = 45 min = 0.75 hours. Let speed be x. 15 min = 0.25 h, 20 min = 1/3 h, 10 min = 1/6 h. Distance = (x * 0.25) + (2x * 1/3) + (x * 1/6) = 39. (1/4 + 2/3 + 1/6)x = 39. (3/12 + 8/12 + 2/12)x = 39. (13/12)x = 39. x = 39 * 12 / 13 = 3 * 12 = 36 kmph.

Multiple choice
  1. 9 hours

  2. 7 hours

  3. 8 hours

  4. 10 hours

  5. 12 hours

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

Downstream speed = 36/3 = 12 km/h. Upstream speed = 36/6 = 6 km/h. Stream speed = (12-6)/2 = 3 km/h. Boat speed = 9 km/h. New stream speed = 3+2 = 5 km/h. New upstream speed = 9-5 = 4 km/h. Time = 36/4 = 9 hours.

Multiple choice
  1. 2 hours

  2. 8 hours

  3. 4 hours

  4. 5 hours

  5. 11 hours

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

Time A = 3x/Va, Time B = 2x/Vb. 3x/Va = 2x/Vb => Va = 1.5Vb. Also Va = Vb + 15. 1.5Vb = Vb + 15 => 0.5Vb = 15 => Vb = 30. New speed of B = 30 + 4 = 34. Time = 170 / 34 = 5 hours.