ok if i got the question right then the average should be an average of the longest possible and the shortest possible. you dont have to add up all the possible values and take the average, just take the extreme small and extreme big and divide by 2
in this case my answer will be (.01+1.99)/2 feet = 1 ft
i chose 0.01 because that's the smallest 2 decimal value and 1.99 because its the largest 2 decimal value  (thats because 4ft long when cut into 2 unequal lenght the smaller should be always less than 2 ft)
i hope thats the right answer

Nepali Kancho, Thanks. 

V2001, the answer would be 10,

you subtract the product of first and second digit from the number.

great