physics high school problem?

Question

hello everybody i got this problem at school that i am like half way into figuring out but i am stuck and i would realy appreciate your help
here is the problem:

A British Concorde(BC) and a French Concorde(FC) flew in opposite direction around the world, a distance of 40 000km. The BC covered half of its flight distance at a speed of 2500 km/h and the other half at a speed of 1000 km/f. The FC spent half of its flight time at 2500 km/h and the other half at 1000 km/h. Which concorde completed the trip first, and by how many hours did it beat the other?

thanks alot for any help

Answer 1

The statement of the problem implies that the rotation of the earth should be ignored since no mention is made as to which plane is flying in which direction.
BC:
t = t1 + t2
t = D1/r1 + D2/r2
t = 20000/2500 + 20000/1000
t = 28.0 hr.

FC:
t1 = t2
D1/r1 = D2/r2
D1/2500 = (40000 - D1)/1000
1000D1 = 100000000 - 2500D1
3500D1 = 100000000
D1 = 28571.4
t1 = 28571.4/2500
t1 = 11.4286hr
t1 + t2 = 2t1 = 22.8572hr
28.0 -22.8572 = 5.1428 hr.
FC wins by 5.1428 hours.

Answer 2

just remember about the spin of the earth, past that i think youll get it by yourself.