Question

A boy travels 50 km with 5km/hr and then for next 4hr travels with a uniform speed of 20 km/hr. What is the average speed for the whole journey?

A. 62/7km/hr.

B. 65/7km/hr.

C. 60/7km/hr.

D. 9km/hr.​

Answer 1

First of all,

Time t1 = s/v = 50/ 5 = 10 hr

Also ,

Distance s2 = v×t = 20 × 4 = 80 km

Therefore ,

Total time = t1 + t2

= 10 + 4

= 14 hr

Total distance = s1 + s2

= 80 + 50

= 130 km

So ,

Average Velocity = Total distance / Total time

= 130 / 14

= 9.28 km/hr

Answer 2

Total Time : - 5 + 4 = 9 Hours

Now, To convert Km/Hour To Metre/Sec.

Multiply The value by 5/18.

So, 50 × 5/18 = 13.888 m/s

Now, 20 × 5/18 = 5.555 m/s

So, Speed = Distance / Time

To Find Distance,

Distance = Speed × Time

= Total Speed = 13.888 + 5.555 = 19.443 m/s

So, Distance = 19.443 × 9 = 175.987 Km

= Average Speed = Total Distance / Total Time

= 175.987 / 9 = 19.554 m/s

Your Answer Is 19.554 m/s

Hope this helps....