Question

a cyclist must travel 800 km how many days will it take if the cyclist travels 8 hours per day going an average speed of 16 km per hour

Answer 1

$\dfrac{16\,\mathrm{km}}{1\,\mathrm h}\cdot\dfrac{8\,\mathrm h}{1\,\mathrm d}=128\,\dfrac{\mathrm{km}}{\mathrm d}$

So if the cyclist travels on average 128 km each day, then it will take

$800\,\mathrm {km}\cdot\dfrac{1\,\mathrm d}{128\,\mathrm {km}}=6.25\,\mathrm d$