Question

A car is travelling with speed of 60km/h and next 20 km ata uniform speed of 80km/h calculate it's average speed.​

Answer 1

Answer:

Time taken to travel 20 km at 60km/hr, t1=20/60=0.33hr

Time taken to travel nxt 20 km at 80km/hr, t2=20/80=0.25hr

Total distance=40 km

Total time=0.58 hr

Average speed=total distance travelled / total time taken=40/0.58=68.96km/hr

Explanation:

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Answer 2

Answer:

average speed = 59.9 km/hr

Explanation:

(i) In the first case, the train travels at a speed of 60 km/h for a time of 0.52 h

Now, Speed =  distance / time = 30km/hr

Distance = 60 x 0.52 = 31.2 km --- i)

 (ii) In the second case, the train travels at a speed of 30 km/h for a time of 0.24 hr.

Now, speed = distance / time = 30 km/hr

Distance = 30 × 0.24 = 7.2 km --- ii)

(iii) In the third case, the train travels at a speed of 70km/h for a time of 0.71 hr.

Now, speed = distance / time = 70km/hr

Distance = 70 × 0.71 hr .

Now speed = distance / time = 70km/hr  

Distance = 70 × 0.71 = 49.7 km ---iii)

From equation 1, 2 & 3 we get,

Total distance travelled

= (31.2 + 7.2 + 49.7) km = 88.1 km .

Total time taken = (0.52 + 0.24 + 0.71) hr = 1.47 hr .

Average speed = Total distance travelled  / Total time taken

= (88.1/1.47) km /hr

Hence, average speed = 59.9 km/hr.