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1.10 Problems * lass A with 40 students has a mean age of 19.7 years. Class B with 60 students has a mean age of 20.3 years. What is the average age of classes A and B combi ined? 2. I n a certain study 300 men averaged 11,000 miles in one year of automobile driving. 200 women av combined? eraged 8000 miles for one year. What is the average of the two groups 3. A salesmen made 40 trips in year 1 and earned a mean of $120 per trip. In year 2 he made 55 trips and earned a mean of $200 per trip. In year 3, 105 trips netted a mean earnings per trip for t 4. An instructor assigns weights of .2, 5, 10 and 2.3 to 4 tests. He grades as follows: A ift > 90; B if 80 < 꿋 < 90; C if 70-, < 80; D if 65 Determine the grades for the following students z < 70, and F if 〈 65. Mr. Armstrong 55, 80, 62, 91 Ms. Brown: 86, 44, 65, 60 Ms. Collins: 91, 80, 97, 92 An investor paid a mean of $3.50 for 100 shares of mutual fund. Later she bought 600 shares at an average price of $2.20 per share. Still later she paid an average of $3.00 per share for 1300 shares. She then sold the lot at an average of $2.79 per share. How did she do?

Answer 1

Solution:-

1) The average age of class A and class B combined is 20.06.

Mean of class A = 19.7, n_A = 40

Mean of class B = 20.3, n_B = 60

$Average = \frac{\bar{x}_{A}\cdot n_{A}&plus;\bar{x}_{B}\cdot n_{B}}{n_{A}&plus;n_{B}}$

$Average = \frac{19.7\cdot 40&plus;20.3\cdot 60}{40&plus;60}$

$Average = 20.06$

11) The mean median and standard deviation is 31360, 34100 and 8277.56 .

$\bar{x} = \frac{\sum x}{n}$

$\bar{x} = \frac{156800}{5}$

Mean = 31360

Median is 34100

$\sigma = \sqrt{\frac{\sum \left ( x-\mu \right )^{2}}{(n-1)}}$

$\sigma = \sqrt{\frac{274072000}{(5-1)}}$

$\sigma = 8277.56$