# Solving puzzles; inspecting computer shipments

A multi choice exam offers 4 choices for each question. Jason guesses the answers, so he has a probability 1/4 of getting any one question correct.

1) What is the expected number of right answers Jason will get if the test has 20 questions?

Data on number of puzzles solved by a person are as follows:

Puzzles solved: 1 2 3 4 5

Probability: 0.2 0.3 0.3 0.1 0.1

1) The probability that a subject solves more than one puzzle is what?

1) A shipment of 500 computers is received. The 500 boxes are labeled 0, 1, 2, 3, ...., 499. THe inspector wishes to test five computers. He uses the table of random digits to choose a single pair of digits at random from all possible pairs 00, 01, .... , 99. It happens that he choose the pair 86. He then inspects all the computers whose labels end in the choosen pair of digits. In this case, he will inspect computers with labels 86, 186, 286, 386, and 486. The chance that the computer labeled 386 would be one of those chosen was what?

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#### Solution Preview

1. Jason has a 0.25 chance of correctly answering each question. There are 20 questions total. Therefore, the expected number of right answers is 0.25*20 = 5.

2. The probability that ...

#### Solution Summary

The inspecting computer shipments for solving puzzles is examined.