A sparse ruler is called optimal if it is both minimal and maximal. Since the number of distinct pairs of marks is m ( m â 1 ) / 2 {\displaystyle m(m-1)/2} , this is an upper bound on the length L {\displaystyle L} of any maximal sparse ruler with m {\displaystyle m} marks.
1 One 23/32-inch 4x8-foot plywood piece weighs approximately 67 pounds, while a piece of OSB of the same dimensions weighs approximately 78 pounds.
There are 32 square feet in a sheet, so a square foot of 1/4 fir plywood weighs about 0.78 pounds. Since 1/2 is twice as thick as 1/4, 1/2 fir plywood weighs twice as much, or 1.56 lbs, and 3/4 three times as much, or about 2.34 lbs. Fir plywood is common, but other species are available.