In metric terms a square foot is a square with sides 0.3048 metres in length. One square foot is the equivalent to 0.09290304 square metres. The six floors of the White House (Washington D.C., U.S.A.) have a combined floor-space area of approximately 55,000 square feet.
A cactus (plural: cacti, cactuses, or cactus) is a member of the plant family Cactaceae within the order Caryophyllales.The word cactus derives, through Latin, from the Ancient Greek ÎºÎ¬ÎºÏÎ¿Ï, kaktos, a name originally used by Theophrastus for a spiny plant whose identity is not certain.Cacti occur in a wide range of shapes and sizes. Most cacti live in habitats subject to at least some drought.actus stems are often ribbed or fluted, which allows them to expand and contract easily for quick water absorption after rain, followed by long drought periods. Like other succulent plants, most cacti employ a special mechanism called  crassulacean acid metabolism  (CAM) as part of photosynthesis.
The tallest free-standing cactus is Pachycereus pringlei, with a maximum recorded height of 19.2 m (63 ft), and the smallest is Blossfeldia liliputiana, only about 1 cm (0.4 in) in diameter at maturity.