Niamh was driving back home following a business trip. She looked at her Sat Nav at 1730
Time
1730
Distance to destination 143 miles
Niamh arrived home at 1942
Work out the average speed of the car, in mph, from 1730 to 1942
You must show all your working.

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?