A covered a distance of 240 km at a certain speed. Had his speed been 8 km/h less, then the time taken would have been one hour more for covering the same distance. How much time (in hours) will he takes to cover a distance of 480 km at his original speed?

$$\eqalign{ & {\text{Distance}} = \frac{{{S_1} \times {S_2}}}{{{S_1} - {S_2}}} \times {\text{difference of time}} \cr & {\text{240}} = \frac{{S\left( {S - 8} \right)}}{{S - S + 8}} \times 1 \cr & 240 \times 8 = S \times \left( {S - 8} \right) \cr & 48 \times 40 = S \times \left( {S - 8} \right) \cr & S = 48{\text{ km/hr}}{\text{.}} \cr & {\text{ = }}\frac{{480}}{{48}} = 10{\text{ hrs}} \cr} $$