It is obviously so unlikely that it would be exactly 290 times out of 400
that the probability would be so close to 0 that it would be negligible.





So we want P(289.5 < x < 290.5)

You can get that with z-scores and a normal table by finding

P(x < 289.5) - P(x < 290.5)

which is

P(z < 5.052) - P(z < 5.154)

Too small to find on any table.  So it has no significance.
It is very nearly impossible, though not quite impossible.

Maybe once in 100 years!

Edwin