Question 350442
distance  of west bound = 4*t = 4t miles t = time
distance of south bound = 2*t = 2t miles
..
Their positions after time t form a right triangle with the starting point. 
8^2 = (4t)^2+(2t)^2
64= 16t^2+4t^2
64=20t^2
64/20 = t^2
16/5 = t^2
take square root
4/sqrt5 = t
t= 1.78 hours