Calculating Arrival Time and Distance for Two Cars on a Highway

[alexistheman]

Two cars travel westward along a straight
highway, one at a constant velocity of
85 km/h, and the other at a constant velocity
of 107 km/h.


a) Assuming that both cars start at the
same point, how much sooner does the faster
car arrive at a destination 18 km away? An-
swer in units of h.
006 (part 2 of 2) 5.0 points


b) How far must the cars travel for the faster
car to arrive 18 min before the slower car?
Answer in units of km.


So i think the answer for problem A) would be .02 h
but I am not Sure exactly if I am doing this right.

 

[alexistheman]

1.78km per min
18/1.78=10.11235955
1.41km per min
18/1.41=12.76595745
12.76595745-10.11235955=2.6535979

 

[alexistheman]

I try to use my relative speed which is 22kph and my distance is 18km, using t = d/r i come up with .818182 but I don't understand how this applys.

 

[planck42]

For your first problem, simply consider how long it takes each individual car to travel 18 km. The second will require a substitution.

 

[alexistheman]

i came up with .04354h and it was right. lol.

 

[alexistheman]

Now i need b)

 

[rl.bhat]

/bump please help!

Let x be the distance.
Find the time taken by two cars to cover that distance. The difference between the times should be 18 minutes.

 

[indep]

lol..we must go to the same school..

 

[alexistheman]

Lol indep, khs possibly?