Assuming you can't simply put the number inside a calculator: write the number as a fraction:
[tex] 0.0625 = \frac{625}{10000} [/tex]
Find the prime factorization both numerator and denominator:
[tex] \frac{625}{10000} = \frac{5^4}{2^45^4} [/tex]
The square root halves the exponents, so the number becomes
[tex] \sqrt{\frac{625}{10000}} = \frac{5^2}{2^25^2} = \frac{25}{100} = 0.25 [/tex]
