Which of the following floppy sizes exists?
5.25 inches is floppy sizes exists.
The 5.25-inch diskettes were available in a capacity of 160 KB single Side, 360 KB low-density and 1.2 MB high-density sizes; by 1994, the 5.25-inch disk was extinct and was replaced by the preferred 3.5-inch disks. The 5 1/4" floppy diskette was really floppy (flimsy), hence the name.
What became the most common format, the double-sided, high-density (HD) 1.44 MB disk drive, shipped in 1986. The first Macintosh computers used single-sided 3½-inch floppy disks, but with 400 KB formatted capacity. These were followed in 1986 by double-sided 800 KB floppies.
In the late 80's, the 5.25-inch floppy disk was on its way out and in 1987 the 3.5-inch floppy disk had moved into the high density category with a capacity of 1.44 MB. You would need 711 1.44 MB floppy disks to equal 1 Gigabyte.
The original floppy disk, a storage media made from a flexible and thin magnetic disk enclosed in a plastic wrapper, was invented in the late 1960s and produced commercially by IBM in 1971. The first disks were a whopping 8 inches across and stored 1.2 MB of data if optimally configured.