40667

For the extension the four numbers are 1,1,3,11. This is because if you times the mean and the the amount of numbers needed you get the amount that all numbers need to add up to. 4x4= 16. 16 is the total. Then you put 11 at the end of the sequences because it is the largest. Next, you know the mode is 1 so you have more than one 1. Also, the range is 10 and 11 is the largest. The difference between 1 and 11 is 10. That's sorted now. Then, the median is 2, so that will be in the middle when the numbers are in order. But when you add 1,1,2,11 you get 15 and 2 is not in the middle. You need to add one more but it could make 5 numbers, which is wrong. You use 3, that still makes 4 numbers overall and still keeps 1 as the mode. So add 1,1,3,11 and you get 16.