A ball is equipped with a speedo meter and launched straight up word. The speedo

4 hours 22 minutes 40 seconds.

Explanation:

Given that the distance, d=400 km, and the average speed, v= 90 km/h.

As the time, t, required to cover a distance, d, with the average speed, v, is

hours

As 1 hour = 60 minutes and 1 minute = 60 seconds.

So, 40/9 hours = 4 hours 22 minutes 40 seconds.

Hence, the time required to travel 400 km with an average speed is 90 km / h is 4 hours 22 minutes 40 seconds.