10. Find the value of the recurring decimal 2.214214....
11. A man purchases a $500 piano by paying monthly installments of $10 and interest on the debt. If the yearly rate is 6%, what is the total amount of interest?
12. The arithmetical mean between two numbers is
and their geometrical mean is 42. Find the numbers. (College Entrance Exam. Board.)
13. If the middle term of
is equal to the fourth term of
