Pls answer it immediately.. i'll mark as

Average = a + b + c + d ... / # of values

70 km/h = 50 km/h + x / 2

140 km/h = 50 km/h + x

90 km/h = x

Therefore, the train would have to travel 90 km/h the second half of its journey. The standard average formula I used to solve this ONLY works when you're dealing with equal weights (Each of the two parts of the journal is 50%). If you are faced with a problem in which the parts of the journey are not equal, you will have to use the formula for weighted average, which would be:

Average = x₁y₁ + x₂y₂ + x₃y₃ + ...

In which x = value and y = relative weight (percentage -> decimal)

You can still use this formula to solve your problem.

70 km/h = (50km/h)(0.50)+ x(0.50)

140 km/h = 50 km/h + x

90 km/h = x

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.