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Mystery Boxes: Breakout Rooms

The boxes below contain 14 numbers, listed in order, of which 6 have been removed. Your job is

to use the clues given to determine the missing numbers. Write your answers in the boxes.

• The mean is 26

• The median is 22

The interquartile range is 20

The mode is 18

. The range is 60

1

4

15

18

29

30

32

58

User Gyre
by
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1 Answer

12 votes
12 votes

Answer:


\begin{array}{ccccccccccccccc}{1} & {3} & {4} & {12} & {15} & {18}& {18 } & {26} & {29} & {30} & {32} & {57} & {58} & {61} \\ \end{array}

Explanation:

Given


\begin{array}{ccccccccccccccc}{1} & {[ \ ]} & {4} & {[ \ ] } & {15} & {18}& {[ \ ] } & {[ \ ]} & {29} & {30} & {32} & {[ \ ]} & {58} & {[ \ ]} \\ \end{array}

Required

Fill in the box

From the question, the range is:


Range = 60

Range is calculated as:


Range = Highest - Least

From the box, we have:


Least = 1

So:


60 = Highest - 1


Highest = 60 +1


Highest = 61

The box, becomes:


\begin{array}{ccccccccccccccc}{1} & {[ \ ]} & {4} & {[ \ ] } & {15} & {18}& {[ \ ] } & {[ \ ]} & {29} & {30} & {32} & {[ \ ]} & {58} & {61} \\ \end{array}

From the question:


IQR = 20 --- interquartile range

This is calculated as:


IQR = Q_3 - Q_1


Q_3 is the median of the upper half while
Q_1 is the median of the lower half.

So, we need to split the given boxes into two equal halves (7 each)

Lower half:


\begin{array}{ccccccc}{1} & {[ \ ]} & {4} & {[ \ ] } & {15} & {18}& {[ \ ] } \\ \end{array}

Upper half


\begin{array}{ccccccc}{[ \ ]} & {29} & {30} & {32} & {[ \ ]} & {58} & {61} \\ \end{array}

The quartile is calculated by calculating the median for each of the above halves is calculated as:


Median = (N + 1)/(2)th

Where N = 7

So, we have:


Median = (7 + 1)/(2)th = (8)/(2)th = 4th

So,


Q_3 = 4th item of the upper halves


Q_1= 4th item of the lower halves

From the upper halves


\begin{array}{ccccccc}{[ \ ]} & {29} & {30} & {32} & {[ \ ]} & {58} & {61} \\ \end{array}

We have:


Q_3 = 32


Q_1 can not be determined from the lower halves because the 4th item is missing.

So, we make use of:


IQR = Q_3 - Q_1

Where
Q_3 = 32 and
IQR = 20

So:


20 = 32 - Q_1


Q_1 = 32 - 20


Q_1 = 12

So, the lower half becomes:

Lower half:


\begin{array}{ccccccc}{1} & {[ \ ]} & {4} & {12 } & {15} & {18}& {[ \ ] } \\ \end{array}

From this, the updated values of the box is:


\begin{array}{ccccccccccccccc}{1} & {[ \ ]} & {4} & {12} & {15} & {18}& {[ \ ] } & {[ \ ]} & {29} & {30} & {32} & {[ \ ]} & {58} & {61} \\ \end{array}

From the question, the median is:


Median = 22 and
N = 14

To calculate the median, we make use of:


Median = (N + 1)/(2)th


Median = (14 + 1)/(2)th


Median = (15)/(2)th


Median = 7.5th

This means that, the median is the average of the 7th and 8th items.

The 7th and 8th items are blanks.

However, from the question; the mode is:


Mode = 18

Since the values of the box are in increasing order and the average of 18 and 18 do not equal 22 (i.e. the median), then the 7th item is:


7th = 18

The 8th item is calculated as thus:


Median = (1)/(2)(7th + 8th)


22= (1)/(2)(18 + 8th)

Multiply through by 2


44 = 18 + 8th


8th = 44 - 18


8th = 26

The updated values of the box is:


\begin{array}{ccccccccccccccc}{1} & {[ \ ]} & {4} & {12} & {15} & {18}& {18 } & {26} & {29} & {30} & {32} & {[ \ ]} & {58} & {61} \\ \end{array}

From the question.


Mean = 26

Mean is calculated as:


Mean = (\sum x)/(n)

So, we have:


26= (1 + 2nd + 4 + 12 + 15 + 18 + 18 + 26 + 29 + 30 + 32 + 12th + 58 + 61)/(14)

Collect like terms


26= ( 2nd + 12th+1 + 4 + 12 + 15 + 18 + 18 + 26 + 29 + 30 + 32 + 58 + 61)/(14)


26= ( 2nd + 12th+304)/(14)

Multiply through by 14


14 * 26= 2nd + 12th+304


364= 2nd + 12th+304

This gives:


2nd + 12th = 364 - 304


2nd + 12th = 60

From the updated box,


\begin{array}{ccccccccccccccc}{1} & {[ \ ]} & {4} & {12} & {15} & {18}& {18 } & {26} & {29} & {30} & {32} & {[ \ ]} & {58} & {61} \\ \end{array}

We know that:

The 2nd value can only be either 2 or 3

The 12th value can take any of the range 33 to 57

Of these values, the only possible values of 2nd and 12th that give a sum of 60 are:


2nd = 3


12th = 57

i.e.


2nd + 12th = 60


3 + 57 = 60

So, the complete box is:


\begin{array}{ccccccccccccccc}{1} & {3} & {4} & {12} & {15} & {18}& {18 } & {26} & {29} & {30} & {32} & {57} & {58} & {61} \\ \end{array}

User ICart
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