£1 = €1.45 If a graph was plotted on the axes below to
show the relationship between pounds and
euros the points (0, a) and (1.5) would
be on the line
Work out the values of a and b

D=distance

VS=velocity through steel

VA=velocity through air

ts=time through steel

ta=time through air

Let's just get some equations out there:

D=VS*ts=16500*ts

D=VA*ta=1100*ta

ta=ts+6 (you can reason that it will take longer through air because the speed is slower)

So, D=16500*ts=1100*ta=D so 16500*ts=1100*ta. Substituting ts+6 in for ta we get 16500*ts=1100*(ts+6), so 16500*ts=1100*ts+6600. Subtracting 1100*ts from both sides, we get 15400*ts=6600, so ts=6600/15400=3/7 seconds. So, to find the distance, we need only plug this time back into the equation D=16500*ts=16500*3/7=7071.43 feet.