The equation which you used is accurate when the transistor is operating in active region. I mean, the current gain or beta value of a transistor at saturation region is different from that at active region, which is less than the former. It means, you cannot put the value as 270, but a lower value. which will cause a higher value of base current. In short, you should know where your BJT is actually operating in; active region or saturation region, and put appropriate value of beta.