The general formula for approximating B(n, p) via a normal distribution is to let the mean be np and the standard deviation be sqrt[n*p*(1-p)]. For this case, n = 225 and p = 1/5.
The mean np = (225)(1/5) = 45, and
The standard deviation sqrt[np(1-p)] = sqrt[(225)(1/5)(1 - 1/5)] = 6
This can be approximated with the normal distributino of mean 45 and SD 6.