Puzzle:
A fly is flying between two trains, each travelling towards each other on the same track at 60 km/h. The fly reaches one engine, reverses itself immediately, and flies back to the other engine, repeating the process each time. The fly is flying at 90 km/h. If the fly flies 180 km before the trains meet, how far apart were the trains initially?
Solution:
Initially, the trains were 240 km apart.
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Solution:
Initially, the trains were 240 km apart.
The fly is flying at the speed of 90 km/h and covers 180 km. Hence, the fly flies for 2 hours after trains started. It's obvious that trains met 2 hours after they started travelling towards each other. Also, trains were travelling at the speed of 60 km/h. So, each train traveled 120 km before they met. Hence, the trains were 240 km apart initially.
4 comments:
240 kms....................rajesh
240 KM
Relative Velocity between trains
Vr = Vt1 + Vt2 = 120km/h
Given Vf = 90km/h
Distance travelled by fly Sf = 180km/h
Sf = Vf * Tf
--> tf = 180/90 = 2 hrs;
So fly flew for 2 hrs.,
since at Tf 2 trians met each other
St = Vr * tf
St = 120 * 2 = 240 Km
so, trains are initially separated by 240 km
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