Answer:
720 kph
Step-by-step explanation:
The ratio of times is ...
new time/original time = (1 2/3 h)/(5 h) = (5/3 h)/5 h) = 1/3
For the same distance, the ratio of speeds must be the inverse of this:
new speed/original speed = s/240 = 1/(1/3) = 3
s = 240(3) = 720 . . . . km/h
The aeroplane must travel at a speed of 720 km/h.
