What age did Mikhail Gorbachev become a member of the Politburo ?
On September 27 , 1985 Nikolai Ryzhkov replaced 79 year old Nikolai Tikhonov as Chairman of the Council of Ministers , effectively the Soviet Prime Minister , and on 14 October 1985 Nikolai Talyzin replaced Nikolai Baibakov as Chairman of the State Planning Committee ( GOSPLAN ) .