Original: Beginning on 20 November 1923 , 1,000,000,000,000 old Marks were exchanged for 1 Rentenmark so that 4.2 Rentenmarks were worth 1 US dollar , exactly the same rate the Mark had in 1914 .
Simplified: The Rentenmark was introduced to stop this problem . The exchange rate was set at 4.2 Rentenmarks to 1 US Dollar .