First of all, we have to convert the time into seconds:
[tex] t=1 ms=0.001 s[/tex]
Light travels at speed of [tex] v=3\cdot 10^8 m/s[/tex].
The distance covered by the light during this time can be found with the formula
[tex]v= \frac{S}{t} [/tex]
where S is the distance covered and t the time. By re-arranging this formula and by plugging the numbers into it, we find how far the light went in 1 millisecond:
[tex]S=vt=(3\cdot 10^8)(0.001 s)=3 \cdot 10^5 m.[/tex]
