Rui Qi starts first at 9:30.
Jaclyn starts later at 10:15.
So 45 minutes=3/4 hour later.
In that 45 minutes Rui Qi has driven already a distance of 3/4 h * 70 km/h=3/4*70 km=52.5 km
So when Jaclyn starts driving the distance between her and Rui Qi is 52.5 km.
Jaclyn drives faster than Rui Qi so that the distance decreases after time.
After t hours distance between Jaclyn and Rui decreases by t*(70-100)=-30 t
So after t hours the distance between J. and R. is
d(t)=52.5-30t
Jaclyn passes Rui Qi at exactly after t hours where the distance d(t) between them becomes 0.
So when d(t)=0
<=>
52.5-30t=0
<=>
t=52.5/30 hours=105/60 hours=105 minutes
So J. passes R. at time 10:15+105 minutes=12 am
RE: Can You Solve?