Answer:
0.000000083333 seconds = 83.333 nanoseconds
Explanation:
The speed of light is approximately 300.000.000 m/s, that means in one second, the light travels 300.000.000 meters.
We can solve that problem using rule of three:
If the light travels 300.000.000 meters in 1 second, to travel 25 meters how long it will take? (let's call the time we want by "T")
300.000.000 - 1
25 - T
300.000.000/25 = 1/T
T = 25/300.000.000
T = 0.000000083333 seconds = 83.333 nanoseconds
