So 210,000,000 are over 18.
21,000,000 can't vote (the 10%).
Leaving us with 189,000,000 possible.
With 147,000,000 registered... (Only 42,000,000 unregistered? Surprising!)
and 50% voting...
73,500,000 generally vote out of a possible 189,000,000, which is:
About 39% of eligible people.