Total distance 5 km; at 5km / 0.65 h =
Second part distance: x; at 6 km/h, during t2
First part distance: 5 - x; at 8.75 km/h, during t1
V = d/t ⇒ t = d/V
t2 = x/6
t1=[5-x]/8.75
t2 + t1 = 0.65
x/6 + [5-x]/8.75 = 0.65
x/6 + 5/8.75 - x/8.75 = 13/20
x/6 - x/8.75 = 13/20 - 5/8.75
x/6 - 4x/35 =13/20 - 20/35
35x - 24x = (35*6)(35*13 - 20*20)/(20*35)
11 x = 16.5
x = 16.5/11 = 1.5 km
D is the answer
hope i helped
Order of the people does not affect the total number of ways. Thus, we use combinations.
Total combinations: 20C5 = 15,504 ways.
Add it together, it should be 1,532,482 (I think)
