Simplify the following text for a Grade 10 native English-speaking person.
Original: Alfred North Whitehead , OM ( 15 February 1861 -- 30 December 1947 ) was an English mathematician who became a philosopher .
Simplified: Alfred North Whitehead , OM ( 15 February 1861 â `` 30 December 1947 ) was an English mathematician who became a philosopher .