In order to make oral calculation fast and accurate, it is a good choice to train with "phonetic oral calculation practice" software. This software can be pronounced by real people, automatically set questions and automatically score. There is also a book called "Fast Algorithm" which is used with software. Practice time is efficient and memory is fast. After practice, your verbal ability can reach the highest level in a short time. After general practice, you can reach about 30 to 50 questions per minute.