Answer: speed is 540 km/h
Step-by-step explanation: Lets mark speed as v.
Because distenace is same, you can mark 6 h · 900 km/h = 10 h · v
and v = 5400 km / 10 h = 540 km/h.
Or using inverse proportions : 10 h / 6 h = v / 900 km/h .
Before multiplying you turn lastproportion around :
10 h / 6 h = 600 km/ h / v ,which gives 10 v = 6 · 900 km/h
and result is same
