At 1:00 PM, Train X departed from Station A on the road to Station B. At 1:40 PM, Train Y departed Station B on the same road for Station A. If Station A and Station B are p miles apart, Train X’s speed is r miles per hour, and Train Y’s speed is s miles per hour, how many hours after 1:00 PM, in terms of p, r, and s, do the two trains pass each other?  Pick:
A) 0.5 + (p - 0.5s)/(r + s)
B) (p - 0.5s)/(r + s)
C) 0.5 + (p - 0.5r)/r
D) (p - 0.5r)/(r + s)
E) 0.5 + (p - 0.5r)/(r + s)
The distance A is going to cover between 1:00 and 1:30   = .5r   now the distance between the two trains = (p-.5r)   the relative velocity = (r-(-s)) = r+s   From 1:30, time is going to take when they meet = (p-.5r)/(r+s)   so the ans is .5+((p-.5r)/(r+s)) [.5 is added for the time from 1:00 to 1:30]   ans is (p - 0.5r)/(r + s)
<result>D</result>
At 1:00 PM, Train X departed from Station A on the road to Station B. At 1:40 PM, Train Y departed Station B on the same road for Station A. If Station A and Station B are p miles apart, Train X’s speed is r miles per hour, and Train Y’s speed is s miles per hour, how many hours after 1:00 PM, in terms of p, r, and s, do the two trains pass each other?