Question

a car travels 30km at uniform speed of 40km/hr and then the next 30km at uniform speed of 20km/hr it average speed=?

Answer 1

Average speed = Total distance / Total time
= (30 km + 30 km) / (t₁ + t₂)
= 60 km / (30/40 hr + 30/20 hr)
= 60 km / (3/4 hr + 3/2 hr)
= 60 km / (3/4 hr + 6/4 hr)
= 60 km × 4 hr / (3 + 6)
= 26.67 kmph

∴ Average speed of car is 26.67 kmph

Answer 2

Hi.

Here is your answer-----

Given conditions-------
Initial speed = 40km/hr.
Final speed = 20km/hr.
Initial distance = 30 km
Final distance = 30 km
Thus, total distance =(Initial + Final)Distance                               
                                = 30 + 30
                                = 60 km
For initial Time (t)= Initial distance/ initial speed
                            = 30/40
                            =3/4 hours.
For final time(T) = Final distance/ Final speed
                          = 30/20
                          = 3/2 hours
Total time = 3/4 + 3/2
                 = (3+6)/4
                 = 9/4 hours..

Using the formula, 
Average speed = total distance/ total time
                         = 60/(9/4)
                         = 26.67 km/hr.

Thus, average speed will be 26.67 km/hr.

Hope this will help u.

Have a nice day.

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