A train X takes 2 hours less than a train Y to cover a distance of 192 km between two cities. Their average speeds differ by 16 km/hr. How long does the faster train take to cover the journey?
A.4 hours✓ Correct
B.5 hours
C.3 hours
D.6 hours
Explanation
Let speeds be u (faster) and v=u-16. 192/v - 192/u = 2, 192·16/(u(u-16))=2, u(u-16)=1536, u²-16u-1536=0, u=(16+√(256+6144))/2=(16+80)/2=48. Time = 192/48 = 4 hours.
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