The sum of your numbers (9.0 + 10.0) is: 21

The difference between your numbers (12.0 - 6.0) is: 6.0

The dividend of your numbers (42.0 / 3.0) is: 14.0

The average of your numbers (1.0 + 7.0 + 3.0 + 8.0 / 4) is: 4.75

The circumference of your circle with a diameter of 4.2 is: 13.194678