05-26-2011, 05:30 PM
Mininolan Wrote:Two trains leave different cities heading toward each other at different speeds. When and where do they meet?
Train A, traveling 70 miles per hour (mph), leaves Kipp Town heading toward Ghost Town, 260 miles away. At the same time Train B, traveling 60 mph, leaves Ghost Town heading toward Kipp Town. When do the two trains meet? How far from each city do they meet?
If:
Each train leaves their respective towns at their constant traveling speed
AND both trains leave at exactly the same time
AND the track between both towns is a single unbroken line
Total distance D = 260
speed Train A Sa = 70
speed Train B Sb = 60
Time T
Trains pass each other when total distance to span = sum of distanced travelled (since AC = AB + BC for any point B that resides on AC (although I cannot remember the name of this rule))
D = Sa*T + Sb*T
260 = 70T + 60T
260 = T(70 + 60)
260 / (70 + 60) = T
T = 2
Trains meet at two hours into their trip.
Kipptrain is Sa*T = 70*2 = 140 miles from kipptown
Ghosttrain is Sb*T = 60*2 = 120 miles from ghosttown
As double-checking, 140 + 120 = 260 miles distance total travelled.
Generic formula D = Sx*T + Sy*T solves this problem. Also works with fighter jets colliding head-on.
Achievements are like the Md after someone's name.
Q: Know what they call a doctor that graduated 800th out of 800 in their class?
A: Doctor.
Q: Know what they call a doctor that graduated 800th out of 800 in their class?
A: Doctor.