Six Sigma is a set of techniques and tools for process improvement. It was introduced by engineer Bill Smith while working at Motorola in 1986. Jack Welch made it central to his business strategy at General Electric in 1995. Today, it is used in many industrial sectors.
One acre equals 0.0015625 square miles, 4,840 square yards, 43,560 square feet or about 4,047 square metres (0.405 hectares) (see below). While all modern variants of the acre contain 4,840 square yards, there are alternative definitions of a yard, so the exact size of an acre depends on which yard it is based.
Acre in Rods and Chains[edit] One Acre is equal to 1 chain by 1 furlong. Noting that 4 rods is a chain, and 10 chain is a furlong, then one acre is also equal to 4 rods by 40 rods (160 squar rods). As one chain is 22 yards, so one acre is also equal to 22 yards by 220 yards (4,840 square yards).