Multiple choice

A motor starts with the speed of 70 km/hr with its speed increasing every two hours by 10 km/hr. In how many hours will it cover 345 km?

  1. $\displaystyle 2\frac {1}{4}$ h
  2. $\displaystyle 4\frac {1}{2}$ h
  3. $4 h \ 5 min$

  4. Cannot be determined
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Hours 1-2: 70 km/hr * 2 = 140 km. Hours 3-4: 80 km/hr * 2 = 160 km. Total = 300 km. Remaining = 45 km. Speed for next interval = 90 km/hr. Time = 45/90 = 0.5 hours. Total time = 2 + 2 + 0.5 = 4.5 hours.

AI explanation

Using the formula distance equals speed multiplied by time, the motor covers 140 km in the first two hours at 70 km/hr and another 160 km in the next two hours at 80 km/hr. The total distance covered in these four hours is 300 km, leaving a remaining distance of 45 km (345 - 300). At the new speed of 90 km/hr, the time taken to cover the remaining 45 km is 0.5 hours, making the total time 4.5 hours.

Keep practicing — related questions