A car moves with a speed of 30 km/h–1 for half an hour, 25 km/h–1 for one hour and 40 km/h–1 for two hours. Calculate the average speed of the car.
Answers
speed = 30km/h
time = 1/2h
distance = 30 * 1/2 = 15km
speed = 25km/h
t = 1h
distance = 25 * 1 = 25km
speed = 40km/h
t = 2h
distance = 40 * 2 = 80km
total distance = 15 + 25 + 80 = 120km
total time = 3.5h
avg speed = 120/3.5 = 34.29km/h(approx)
Answer:
The car moves with the speed of 30 km/hr for a time of 1/2 hours .
Speed (s) = 30 km/hr .
Time (t) = 1/2 hr
Distance (d) = ?
Distance = speed × time
⇒ d = s × t
⇒ d = 30 km/hr × 1/2 hr
⇒ d = 30/2 km
⇒ d = 15 km
The car moves with the speed of 25 km/hr for a time of 1 hour .
Speed (s) = 25 km/hr .
Time (t) = 1 hr
Distance (d) = ?
Distance = speed × time
⇒ d = s × t
⇒ d = 25 km/hr × 1 hr
⇒ d = 25 km
The car moves with the speed of 40 km/hr for a time of 2 hours .
Speed (s) = 40 km/hr .
Time (t) = 2 hr
Distance (d) = ?
Distance = speed × time
⇒ d = s × t
⇒ d = 40 km/hr × 2 hr
⇒ d = 80 km
Total distance = 80 km + 25 km + 15 km
⇒ Total distance = 120 km
Total time = ( 1/2 + 1 + 2 ) hr
⇒ Total time = ( 3 + 1/2 ) hr
⇒ Total time = 7/2 hr
Average speed = total distance / total time
⇒ Average speed = 120 km / 7/2 hr
⇒ Average speed = 240/7 km/hr
The average speed ≈ 34.29 km/hr .
Explanation:
▶ We know that speed is the distance travelled in unit time . Hence we can represent Speed = distance / time and from this formula we get distance = speed × time . Total distance is calculated by using this formula at all phases and then total time is found out . Then we calculate the average .