posted by anonymous .
How long does it take an automobile traveling in the left lane of a highway at 70.0 km/h to overtake (become even with) another car that is traveling in the right lane at 20.0 km/h when the cars' front bumpers are initially 110 m apart?
let the distance needed to pass be x km
so the time taken by the slower car = x/20
and the time taken by the faster car = (x+.110)/70
but those times are equal, so ....
x/20 = (x+.110)/70
70x = 20x + 2.2
50x = 2.2
x = 2.2/50 = .044
time taken by slower car to be overtaken = .044/20
= .0022 hours
= 7.92 seconds
notice .044/20 = .0022
and (.044 + .110)/70 = .0022