Expert please help

Dear Student,
Distance between Delhi and Agra, d = 200 km
A train travelled the first 100 km at a speed of 50 km/h
Time taken to travel frist 100 km = 100/50 = 2 hrs.
Let the train travels the rest of the 100 km at a speed of v km/h.
Time taken to complete the rest 100 km = 100/v hrs.
Total distance, d = 200 km
Total time taken, $t = 2 + \frac{100}{v}$
Average speed = $\frac{total dis\tan ce travelled}{total time taken}=\frac{d}{t}=\frac{200}{2+100/v}=70 km/h \left(Given\right)$
$$\begin{gathered} 200=70\left(2+\frac{100}{v}\right) \\ 200-140=\frac{7000}{v} \\ 60=\frac{7000}{v} \\ v=\frac{7000}{60}=\frac{350}{3}km/h=116.7 km/h \end{gathered}$$

Regards
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