C in the refractive index formula isn't equal to 3x10^8

Question

Refractive index = c/v so c = Refractive index*v. if v = 2.29 x 10^8 and refractive index = 1.31 then c = 1.31*2.29x10^8, the answer comes = 299990000 but as we know c = 3*10^8 which is 300000000, sorry if this is dumb but im new to this and I have no idea why is the value of c different

Answer 1

"c" refers to the speed of light in a vacuum. It is not exactly equal to 3*10^8 m/s, but it's close enough that we frequently use it as an approximation in classroom settings. The speed of light in a vacuum is more precisely 2.99792458*10^8 m/s.