sqrt(24*sqrt(30

I hope that you realise happy - your answer is an approximation.  It is not exact :)

You are learning to use the calculator very efficiently - well done :))

$${\sqrt{{\mathtt{24}}}}{\mathtt{\,\times\,}}{\sqrt{{\mathtt{30}}}} = {\mathtt{26.832\: \!815\: \!729\: \!997\: \!476\: \!4}}$$