RRB Group D 3-Oct-2018 Shift 3 Solved Paper

A train is travelling at a certain speed from its originating station. After 2 hours, another train starts from the same station and travels at a speed of $70\mathrm{km}∕\mathrm{h}$ in the same direction as the previous train and catches up with the first train after 5 hours. What is the speed of the first train in $\mathrm{km}∕\mathrm{h}?$