Measures of central tendency are numbers used to represent a set of data.  
  Three types of measures of central tendency are mean, median, and mode.
    Mean:  Average  (add all numbers and divide by the number of numbers)
    Median:  The middle number when the numbers are arranged in order.
    Mode:  The number (or numbers) that occur the most often.
    Example 1 Mean
    The lengths in minutes of five summer movies are shown below. 
    What is the mean length of the movies?
           125, 100, 150, 120, 110
    mean =  125100150120110     605  121
                                  
                     5               5
         The mean length of the movies is 121 minutes.
  Example 2 Median
  The list below shows the cost of general admission to eight different zoos. 
  Find the median of the data.
    $8, $10, $12, $6, $5, $12, $9, $10
   Arrange in order then find the middle number.
          $5, $6, $8, $9, $10, $10, $12, $12
                910 19
                     9.5
                 2  2
     The median cost of general admission to the zoos is $9.50.
    Example 3 Mode
    The table shows the number of kittens sold at a pet store during a 10-day 
    period. What is the mode of the data?           Kittens Sold
                                              4    1     2    4    3
                                              6    4     3    0    4
     4 occurs four times. 3 occurs twice. All the other numbers occur once.
                      Since 4 occurs most frequently, the mode 
                      number sold is 4.
 Example 4 Mean
 Dominic rode his bike 5 miles on Monday, 3 miles on Tuesday, 8 
 miles on Wednesday, and 5 miles on Thursday. How many miles 
 must Dominic ride on Friday so that the average number of miles 
 (mean) for all five days is 6 miles?
       sum   6MondayTuesdayWednesday ThurdayFriday
   mean =  #of           5
             65385F
                 5
             621F    3021F
            5                     5
                5
                    9 miles are needed on Friday.