250(1/2)^(10/2)

$${\mathtt{250}}{\mathtt{\,\times\,}}{\left({\frac{{\mathtt{1}}}{{\mathtt{2}}}}\right)}^{\left({\frac{{\mathtt{10}}}{{\mathtt{2}}}}\right)} = {\frac{{\mathtt{125}}}{{\mathtt{16}}}} = {\mathtt{7.812\: \!5}}$$

.

$$\\250(1/2)^{10/2}\\\\
=250*(\frac{1}{2})^5\\\\
=250*\frac{1}{32}\\\\
=\frac{125}{16}\\\\
=7\frac{13}{16}\\\\$$

.