First of all, we have to convert the time into seconds:
\(t=1 ms=0.001 s\)
Light travels at speed of \(v=3\cdot 10^8 m/s\).
The distance covered by the light during this time can be found with the formula
\(v= \frac{S}{t}\)
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:
\(S=vt=(3\cdot 10^8)(0.001 s)=3 \cdot 10^5 m.\)
