Chapter Exercise 572 A certain model of remotecontrol garage

Chapter Exercise 5-72

A certain model of remote-control garage door opener has thirteen binary (off/on) switches. The homeowner can set any code sequence.

How many separate codes can be programmed?

If you try to use your door opener on 1,000 other garages, how many times would you expect to succeed? (Round your answer to nearest integer.)

Chapter Exercise 5-84

A web server hosting company advertises 99.999 percent guaranteed network uptime.

How many independent network servers would be needed if each has 92 percent reliability? (Round your answer to the nearest whole number.)

How many independent network servers would be needed if each has 85 percent reliability? (Round your answer to the nearest whole number.)

Solution

there are 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 = 2 ^ 9 = 512 different sequences

you should expect if you randomly try your opener on 1000 doors that at least one will open.

1000/512 = 1.953125 is the actual expected number of doors you\'d except to open.