Jack and Joe leave their homes at the same time and drive toward each other. Jack drives at 80 mph, while Joe drives at 30 mph. They pass each other in 10 minutes. How far apart were Jack and Joe when they started?
Jack speed = 80mph
Joe speed = 30 mph
travelling towards each other
so speed = 30+80 =110 mph.
let distance be x when they start.
time take = 10 minutes = 1/6 hour
d= 18 1/3 miles.
Just simple kinematics,
Jack = v1 = 60 mph
Joe = v2 = 30 mph
t = 10 min = 1/6 hr
Jack Dist = (60 mph) * (1/6 hr) = 10 miles
Joe Dist = (30 mph) * (1/6 hr) = 5 miles
Total Distance Between = 15 miles
If you have trouble imagining points starting from some unknown and traveling to a mid point, just imagine it as if they started from some point then traveled away in the same manner, how far apart the would be.