My silver maple tree is 11 feet in circumference. Any idea how old it is?

Answer 1

Like the red maple, silver maple is a relatively short-lived tree when compared to the sugar or black maple, living perhaps
http://www.massmaple.org/treeID.html

130-150 years. Because of its fast growth rate, however, mature trees can achieve diameters in excess of 3 feet and heights in excess of 100 feet. On good sites with little competition from other trees, silver maple diameter growth may approach 1/2 inch per year (rates as high as 1 inch per year have been recorded). Silver maple's growth rate often responds dramatically to thinning or release cutting.
Open Link below...........
How to figure diameter of tree by the circumference, it is determined by the breast height/see diagram of direction of growth.
http://www.pfmt.org/inventories/diameter.htm

Answer 2

Use these links to see if they help.

Answer 3

Cut it open and count the ring things.....