Assuming that ZFC is consistent, the existence of strongly inaccessible cardinals provably cannot be proved in ZFC.
... the age of 18, 5.1% from 18 to 24, 32.6% from 25 to 44, 31.2% from 45 to 64, and 9.4% who are 65 years of age or older. The median age is 42 years. For every 100 ...