Mathematical and Physical Journal
for High Schools
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# Problem G. 653. (December 2018)

G. 653. One morning two locomotives start from the engine shed and travel in the same direction. The first one is a diesel engine and has a speed of 90 km/h, whilst the other one is an electric engine, which started 1.5 minutes after the diesel engine, and has a speed of 20 m/s. 10 minutes after the diesel engine started it meets a fast train coming along the neighbouring track in the opposite direction. What is the speed of the fast train if it meets with the electric engine 1.5 minutes after it met with the diesel one?

(3 pont)

Deadline expired on January 10, 2019.

Sorry, the solution is available only in Hungarian. Google translation

Megoldás. A dízelmozdony 10 perc alatt 90/6=15 kilométert tesz meg, a dízelmozdony és a gyorsvonat találkozása tehát a mozdonyszíntől 15 km-nyire történt. A villanymozdony is 10 percig haladt az indulásától a gyorsvonattal való találkozásáig, ezalatt 12 km-t tett meg. A két találkozási pont távolsága 3 km, ezt a gyorsvonat másfél perc, vagyis $\displaystyle \tfrac1{40}$ óra alatt tette meg. A gyorsvonat sebessége tehát 120 km/h.

### Statistics:

 96 students sent a solution. 3 points: 77 students. 2 points: 11 students. 1 point: 3 students. Unfair, not evaluated: 1 solutions. Not shown because of missing birth date or parental permission: 4 solutions.

Problems in Physics of KöMaL, December 2018