Chapter 12.3, Problem 20PPS

To determine

To calculate: the probability that there will be no quizzes during a five day week

Answer to Problem 20PPS

The required probability is 0.1944

Explanation of Solution

Given information:

Mr. Woodruff gives a pop quiz at the beginning of class 15% of the time.

Calculation:

The fire drill can be between 8: 30 and 3: 00 A.M (between 390 minutes). So the probability that fire drill is in afternoon (that is between $12:00\text{pm}$ and 3: 00 am) is,

P (in afternoon) $=\frac{180}{390}$

And the probability that fire dill is between 1: 20 to 1: 55 is

P (between 1: 20 to 1: 55) $=\frac{35}{390}$

The probability that it will start during the test is,

  $\begin{array}{l}P(\text{start during the test})=\frac{P(\text{between}1:20\text{to}1:55)}{P(\text{in afternoon})}\\ =\frac{35/390}{180/390}\\ =0.1944\end{array}$

Hence, the required probability is 0.1944