Question

covers a distance of 50 km with speed 20 km per hour and next 75 km with the speed of 50 km per hour calculate average speed

Answer 1

Hi.

Here is your answer---

__________________

Given---

Initial Distance(d1) = 50 km.
Initial Speed(u) = 20 km/hr.

Using the Formula,
   
              Speed = Distance/Time.
              

Thus, Initial Time(t1) =  50/20
                                  = 5/2 hr.

Final Distance(d2) = 75 km.
Final Speed(v) = 50 km/hr.

Thus, Final Time(t2) = 75/50
                                 = 3/2 hr.

For Average Speed,

  Total Distance(d) =  d1 + d2
                              = 50 + 75
                              = 125 km.

  Total Time(t) = t1 + t2
                       = 5/2 + 3/2
                       = ( 5 + 3)/2                           [Taking L.C.M.]
                       = 8/2 
                       = 4 hr.

Using the Formula,

Average Speed = Total Distance/Total Time
                          = 125/4
                          = 31.25 km/hr.

Thus, Average Speed is 31.25 km/hr.

__________________

Hope it helps.

Have a nice day.