10. (−2 1/2)² : (0,25)² · ((−5)⁻²)²

\[-2\frac12=-\frac52,\qquad \left(-\frac52\right)^2=\frac{25}{4},\qquad (0.25)^2=\frac1{16}.\]

Кроме того:

\[((−5)^{-2})^2=5^{-4}=\frac1{625}.\]

Тогда:

\[\frac{25}{4}:\frac1{16}\cdot\frac1{625}=100\cdot\frac1{625}=\frac4{25}.\]

Ответ: \(\frac4{25}\)