Simplify the following text for a Grade 8 native English-speaking person.
Original: Between the fifteenth and the nineteenth centuries ( 500 years ) , the Atlantic slave trade took an estimated 7 â `` 12 million slaves to the New World .
Simplified: Between the 15th and the 19th centuries ( 500 years ) , the Atlantic slave trade took an estimated 7 â `` 12 million slaves to the New World .