MA 111 Review for Exam 2 Exam 2 given in class on Tuesday March 2 will cover numbers and quantities percent and percent change mean and median and the introduction to indices Can you work each homework worksheet and quiz problem correctly and quickly providing explanations and justifications without looking at the text or your notes Have you carefully studied the material in the text You should be familiar with the following key ideas Understand the difference between number and quantity Know how to convert units e g miles hour to feet sec Know how to compare quantities with ratios and with percents Know how to understand or make better sense of very large or very small quantities Understand the importance of correct units Understand what percent means Know what the base of a percent is and be able to identify the base of a percent in context Be able to find different variables in a percentage calculation e g use the base and the result to find the percent Understand how changes in numbers can be measured by percents percent change Know how to increase or decrease a number by a percentage and how to reverse this process Understand the difference between 1 change 2 percent change 3 change in percent percentage points and 4 percent change of percent Understand the difference between mean and median and know how to compute them and to solve problems involving these quantities Be able to create an index from a collection of data to figure out the index values from data values and to figure out data values from index values Be able to interpret a short passage and analyze the given information about numbers quantities percents percent change means medians and indices 1 Practice Problems 1 Review the practice problems for Exam 1 and also the problems from Exam 1 itself 2 A data set of 10 numbers has mean 40 What is their sum 3 A data set of 8 numbers has mean 50 The data set is enlarged by introducing a 9th number 14 What is the new mean 4 A data set of 5 numbers has mean 88 What is the smallest value of a sixth number that can be introduced into the data set to raise the mean to 90 5 A data set of 11 numbers has median 12 How many numbers in the data set are less than 12 How many numbers in the data set are less than or equal to 12 How do your answers change if you know that all of the numbers in the data set are different 6 Ask a friend to give you two different numbers a and b Construct a data set with mean a and median b With mean b and median a 7 Below is a partial table of an index for the cost of a gallon of fuel oil Fill in the missing numbers Year Cost of gallon of oil Cost of Oil Index 2006 2 418 2007 18 88 2008 26 60 2009 2 509 20 00 2010 2 967 2
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