IBM 729 the tape reel. A 3/4 inch gap between records allowed the mechanism enough time to stop the tape. Initial tape speed was 75 inches per second (2.95 m/s) and recording density was 200 characters per inch, giving a transfer speed of 120 kbit/s. Later 729 models supported 556 and 800 characters/inch (transfer speed 480 kbit/s). At 200 characters per inch, a single 2400 foot tape could store the equivalent of some 50,000 punched cards (about 4,000,000 six-bit bytes, or 3 MByte). The 729 series was superseded by 9 track tape drives introduced with the IBM System/360. The IBM 729 I
Cube root solution expressions involve the real cube root of a real number, while if all three solutions are real numbers then they may be expressed in terms of the complex cube root of a complex number. Quartic equations can also be solved in terms of cube roots and square roots. The calculation of cube roots can be to traced back to Babylonian mathematicians from as early as 1800 BCE. In the fourth century BCE Plato posed the problem of doubling the cube, which required a compass-and-straightedge construction of the edge of a cube with twice the volume of a given cube;