A train takes $5$ hours at $48$ km/h to cover a distance. To cover the same distance in $4$ hours, its speed…

A train takes $5$ hours at $48$ km/h to cover a distance. To cover the same distance in $4$ hours, its speed must be:
  1. $54$ km/h
  2. $56$ km/h
  3. $60$ km/h
  4. $64$ km/h

Solution

Speed $\times$ time constant: $48 \times 5 = s \times 4 \Rightarrow s = 60$ km/h.

Asked in: IMO

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