Thereâs really no way to say exact costs for sure but here in the DC area, youâre most likely starting at $5,000-10,000 for a smaller backyard pond and going up from there. One like the pond above â where we brought in literally dozens of truckloads of soil and stone â would be well north of $30,000-40,000.
In 1706 (a fruitful year for Pi), Machin found this rapidly converging formula for its calculation: Ï/4 = 4 x arctan (1/5) - arctan (1/239). Also in 1706, the Welshman, William Jones, became the first person to use the Greek letter Ï as an abbreviation for the periphery of a circle with unit diameter. Euler adopted the symbol, and it quickly became the standard notation for Pi in all mathematical contexts.
The young French mathematician Blaise Pascal (1623-1662) invented the first adding machine in 1642, a clever device driven by gears and capable of performing mechanical addition and subtraction. The first commercially successful adding machine was developed in 1886 by William Seward Burroughs (1855-1898).