The longest river in the uk is the river severn which has a length of 24 cm on a map. if the map is drawn at a scale of 1: 1,500,000, then how many kilometers is the river actually?

Assume that there is a 11% rate of disk drive failure in a year. a. if all your computer data is stored on a hard disk drive with a copy stored on a second hard disk drive, what is the probability that during a year, you can avoid catastrophe with at least one working drive? b. if copies of all your computer data are stored on four independent hard disk drives, what is the probability that during a year, you can avoid catastrophe with at least one working drive?