Friday, January 10, 2014

Math POTW #14



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5 comments:

  1. Hello.

    My sister and I did this together.

    Our first step was to find all the possible integers based on the 4 given digits (2,0,1,4)

    In the end, we came up with 18 different integers. We double checked by arranging them from least to greatest and by using place value. Through this, we can identify whether or not we missed any other possible integers. The numbers were:

    1024, 1042, 1204, 1240, 1402, 1420, 2014, 2041, 2104, 2140, 2401, 2410, 4012, 4021, 4102, 4120, 4201, 4210.

    A pattern we noticed from this is that the tens and ones always switch with every upcoming thousands and hundreds pair.

    e.g

    1024,1042 (10 is the thousands/hundreds) *Note how the last two digits switch

    We realized how this applied to the other integers. So, we used it to ensure we had all the right numbers.

    Average of least and greatest = 2617

    (4210 + 1024) / 2

    Median of all possible integers = 2122

    *note that when finding the median, there were two remaining numbers, 2104 and 2140.

    (2104 + 2140) / 2

    The difference = 495

    2617 - 2122 = 495

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  2. 1024 is the smallest
    4210 is the biggest
    2617 is the average of the smallest(1024) and the biggest(4210)
    1024,1042,1204,1240,1402,1420,2014,2041,2104,2140,2401,2410,4012,4021,4102,4120,4201,4210
    The median is 2270.5

    ReplyDelete
    Replies
    1. Can you please explain to me how 2270.5 is the median? I got a different answer.

      Delete
  3. First I decided to find all the possible number?integers can be made with 2014.
    1024
    1042
    1204
    1240
    1402
    1420
    2014
    2041
    2104
    2140
    2401
    2410
    4012
    4021
    4102
    4120
    4201
    4210
    2. With this I figured that all these numbers had a basic pattern of switching numbers.
    The smallest number was 1024
    The largest number was 4210.

    The average of the largest and smallest numbers was
    1024+4210= 5234
    5234/2=2617

    The median of all the integers was 2270.5 rounded to 2271

    (First I roganized this from the least to greatest and then I found the central number)
    1024, 1042, 1204, 1240, 1402, 1420, 2014, 2041, 2104, 2140, 2401, 2410, 4012, 4021, 4102, 4120, 4201, 4210


    ReplyDelete
  4. Good job everyone. Remember to check-on on the site even after you've provided an answer because your peers may be asking you questions.

    Solution
    First, we will determine the average of the largest and smallest numbers.
    With a given set of four digits, the largest possible integer that can be formed puts the largest
    digit in the thousands place, the second largest digit in the hundreds place, the third largest
    digit in the tens place, and the smallest digit in the units place. That is, the largest integer is
    formed by putting the digits in decreasing order from the thousands place to the units place.
    This is because the largest digit can make the largest contribution in the place with the most
    value. Thus, the largest integer that can be formed with the digits 2, 0, 1, 4 is 4210.
    Similarly, with a given set of digits the smallest integer is formed by putting the digits in
    increasing order from the thousands place to the units place. Here, there is an added wrinkle
    that the integer must be at least 1000. Therefore, the thousands digit is at least 1. The
    smallest integer of this type that can be made uses a thousands digit of 1, and then lists the
    remaining digits in increasing order. This integer is 1024.
    Therefore, average of the largest and smallest numbers is 2617.
    Now, let's determine the median of all of the numbers that can be created.
    Since the thousands digit is at least 1, the smallest numbers will begin with a 1. The
    remaining digits will be 0, 2 and 4, in some order. There are six possibilities for the remaining
    digits: 024, 042, 204, 240, 402, or 420. Therefore, there are six numbers that begin with a 1.
    Similarly, there are six numbers that will begin with a 2 and six numbers that will begin with a
    4. Therefore, there are 18 di erent numbers that can be created this way. The smallest six
    numbers will begin with a 1 and the largest six numbers will begin with a 4. The middle six
    numbers will begin with a 2 and the median of all of the numbers will equal the median of the
    middle six numbers. The middle six numbers, from smallest to largest, are
    2014; 2041; 2104; 2140; 2401; 2410
    Since there is an even number of numbers, the median of these six numbers is the average of
    the middle two, which is 2122. Therefore, the median of all of the numbers is
    2122. (Alternatively, we could have listed out all 18 numbers that can be created this way in
    order to determine the median.)
    The di erence between the average of the largest and smallest numbers and the median of all
    numbers is therefore 2617 - 2122 = 495.

    ReplyDelete