The airliner concorde flies 2000km at a speed of 1600km/hr and then returns due to bad weather at a speed of 1000km/h find the average speed for the whole trip ,

Step 1:
Compute for the time in speed 1 & 2.
t1=d/s
=2000km/(1600km/hr)
=1.25hrs
Since, the airline just returned: therefore, the distance is the same.
t2=d/t
=2000km/(1000km/hr)
=2hrs

Step 2:
Solve for the total time and distance.
Ttotal=t1+t2
=(1.25+2)hrs
=3.25hrs
Since, it's a round trip, just add the distances:
Dtotal=2(2000km)
=4000km

Step 3:
Solve for the Average Speed.
Average Speed=DTotal/Ttotal
=4000km/3.25hr
=1230.77 km/hr

Hope it helped. :)