It is given in the question that, a rocket travels 2.8x10^4 km h^-1.
It means in one hour, the rocket travels
[tex] 2.8* 10^4km. [/tex]
And we have to find how much the rocket travels in 5 hours, and for that we have to do multiplication, that is
[tex] 2.8*10^4 *5 = 14*10^4 = 1.4* 10^5 km [/tex]
