Question 894874

change 500 meters to kilometers 
500 meters is 1/2 k
(80+r)*(30/3600)-(80*30/3600)=1/2

30r/3600=1/2

r/120=1/2
r=60
so the second car was going 80+60=140 kph
check
(140)*(30/3600)-(80*30/3600)=1/2

7/6-4/6=3/6
3/6=1/2 km
ok



The other tutor didn't read the question correctly.

The key is that the problem states that the second car passes the first car.
A car going 20 kph will NOT pass a car going 80 kph