How long does it take for light to traverse the diameter of the galaxy?

Decision.
Since light moves rectilinearly and uniformly with a speed of c ≈ 299792458 m / s, then to calculate the time of its motion t we use the formula t = S: s, where S is the distance it has traveled. From the condition of the problem it is known that light crosses our Galaxy along its diameter, the value of which is found in the reference literature S = 946073047258080000000 m. Substitute the values of physical quantities in the calculation formula and make calculations: t = 946073047258080000000: 299792458 (seconds); t = 100,000 years.
Answer: Light takes 100,000 years to cross the Galaxy across its diameter.