Question 983699
L, length of the procession in meters


{{{5(km/hour)*(80/60)(hours)=L}}}
{{{L=5(4/3)*kilometers}}}


Let's change the meaning of L in the units.
Now, say L is to be in meters.
{{{L=5(4/3)*1000*meters}}}


Ten persons per meter:
{{{((5*4*1000)/3)*meters*(10/1)(persons/meter)}}}
{{{20*1000*10/3}}}
{{{(2/3)*10000}}}
{{{highlight(66667)}}} persons; maybe more accuracy than meaningful.


Better, about between  66600 and 66700 persons.