Let $\mu$ be a Lebesgue measure on the Borel $\sigma$ algebra.
Then is $\mu( [0,\frac{1}{4}) \bigcup [\frac{3}{4},1])$ just $\mu([\frac{3}{4},1]) + \mu([\frac{3}{4},1])$
with $\mu( [0,\frac{1}{4})) = \frac{1}{4} - 0 = \frac{1}{4}$
and $\mu([\frac{3}{4},1]) = 1 - \frac{3}{4} = \frac{1}{4}$?