• # question_answer A train does a journey without stopping in 8 hours. If it had travelled 5 km an hour faster, it would have done the journey in 6 hours 40 min, its slower speed is A)  32 km/hr B)  25 km/hr C)  28 km/hr           D)  40 km/hr

[b] Let slower speed = u km/hr. As the distance is fixed $u\times 8=(u+5)\times \frac{20}{3}\,\,\,\,[\because 6\,hr\,\,40\,\min =6\,hr+\frac{40}{60}\,hr$ $=6\frac{2}{3}=\frac{20}{3}\,hrs.]$ $\Rightarrow$ $24\,u=20\,u+100$ $\Rightarrow$ $4\,u=100$ $\Rightarrow$ $u=25\,km/hr$