Simplify the following text for a Grade 6 native English-speaking person.
Original: George Grenville ( 14 October 1712 â `` 13 November 1770 ) was a British Whig statesman who rose to the position of Prime Minister of Great Britain .
Simplified: George Grenville ( 14 October 1712 â `` 13 November 1770 ) was Prime Minister of Great Britain . He was a member of the Whig Party .