Time, Speed and Distance Questions

Multiple choice
  1. 28

  2. 30

  3. 20

  4. 42

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

Time for engine to reach A = 20 km / 30 km/h = 2/3 hours. Insect speed = 42 km/h. Distance = Speed * Time = 42 * (2/3) = 28 km.

Multiple choice
  1. $0.6$
  2. $0.8$
  3. $0.9$
  4. $0.4$
  5. $0.5$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let T be the total time. Distance with cabbage = (3/4)T * 6 = 4.5T. Distance without cabbage = (1/4)T * 12 = 3T. Total distance = 4.5T + 3T = 7.5T. Fraction = 4.5T / 7.5T = 4.5 / 7.5 = 0.6.

Multiple choice
  1. $6$ miles per hour
  2. $6.5$ miles per hour
  3. $7$ miles per hour
  4. $7.5$ miles per hour
  5. $8$ miles per hour
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Let speed be v. Time to house = 2/v. Return speed = v - 4. Return time = 2/(v-4). Total time = 45 min = 0.75 hours. 2/v + 2/(v-4) = 0.75. 2(v-4 + v) / (v(v-4)) = 0.75. 2(2v-4) = 0.75(v^2 - 4v). 4v - 8 = 0.75v^2 - 3v. 0.75v^2 - 7v + 8 = 0. Multiply by 4/3: v^2 - 9.33v + 10.66 = 0. Roots are 8 and 1.33. Since speed must be > 4, v = 8.

Multiple choice
  1. $5$ minutes
  2. $6$ minutes
  3. $8$ minutes
  4. $10$ minutes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Time for A = 25 miles / 50 mph = 0.5 hours = 30 minutes. Time for B = 25 miles / 60 mph = 25/60 hours = 25 minutes. Difference = 30 - 25 = 5 minutes.

Multiple choice
  1. $67$
  2. $134.4$
  3. $145.9$
  4. $160$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let car speed be v. Train speed is 1.4v. Time for car = 140/v. Time for train = 140/(1.4v) + 25/60. Since times are equal: 140/v = 100/v + 5/12. 40/v = 5/12, so v = 96 km/hr. Train speed = 1.4 * 96 = 134.4 km/hr.

Multiple choice
  1. $4:21$
  2. $3:22$
  3. $1:4$
  4. $3:5$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let distances be d1 and d2. Average speed = Total Distance / Total Time = (d1+d2) / (d1/20 + d2/70) = 50. (d1+d2) / ((7d1+2d2)/140) = 50. 140(d1+d2) = 50(7d1+2d2). 14d1 + 14d2 = 35d1 + 10d2. 4d2 = 21d1. d1/d2 = 4/21.